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Hydroponics basically means working water ("hydro" means "water" and "ponos" means
"labor"). Many different civilizations have utilized hydroponic growing techniques throughout
history. As noted in Hydroponic Food Production (Fifth Edition, Woodbridge Press, 1997, page
23) by Howard M. Resh: "The hanging gardens of Babylon, the floating gardens of the Aztecs of
Mexico and those of the Chinese are examples of 'Hydroponic' culture. Egyptian hieroglyphic
records dating back several hundred years B.C. describe the growing of plants in water."
Hydroponics is hardly a new method of growing plants. However, giant strides have been
made over the years in this innovative area of agriculture.

Throughout the last century, scientists and horticulturists experimented with different methods
of hydroponics. One of the potential applications of hydroponics that drove research was for
growing fresh produce in nonarable areas of the world. It is a simple fact that some people
cannot grow in the soil in their area (if there is even any soil at all). This application of
hydroponics was used during World War II. Troops stationed on nonarable islands in the
Pacific were supplied with fresh produce grown in locally established hydroponic systems.

Later in the century, hydroponics was integrated into the space program. As NASA considered
the practicalities of locating a society on another planet or the Earth's moon, hydroponics easily
fit into their sustainability plans. This research is ongoing. But by the 1970s, it wasn't just
scientists and analysts who were involved in hydroponics. Traditional farmers and eager
hobbyists began to be attracted to the virtues of hydroponic growing. A few of the positive
aspects of hydroponics include:
• The ability to produce higher yields than traditional, soil-based agriculture.
• Allowing food to be grown and consumed in areas of the world that cannot support crops in
the soil.
• Eliminating the need for massive pesticide use (considering most pests live in the soil),
effectively making our air, water, soil, and food cleaner.

Commercial growers are flocking to hydroponics like never before. The ideals surrounding
these growing techniques touch on subjects that most people care about, such as helping end
world hunger and making the world cleaner. In addition to the extensive research that is going
on, everyday people from all over the world have been building (or purchasing) their own
systems to grow great-tasting, fresh food for their family and friends. Educators are realizing
the amazing applications that hydroponics can have in the classroom. And ambitious
individuals are striving to make their dreams come true by making their living in their backyard
greenhouse, selling their produce to local markets and restaurants.

And now that so many people from so many different walks of life are involved in hydroponics
and its associated disciplines (such as aeroponics and aquaponics), progress is coming
faster than ever before.

2. What is Hydroponics?

While the true definition varies from expert to expert, hydroponics is basically the growing of
plants without soil. The word “Hydroponic” is derived from the Greek words – “Hydro” which
means water and “Ponos” which means labor. True hydroponics is growing plants in water
without any type of media e.g. NFT and Aeroponic, however, growing plants in soilless media
such as coco, perlite rockwool etc are also classified as hydroponics.

3. What is pH, and how can I test for it?

pH stands for “Potential of Hydrogen” and is the symbol for the hydrogen ion (H+) in liquids. pH
has a range from 0 (acidic) -14 (alkaline), with 7 being neutral. For hydroponics we are aiming
for a pH between 5.5 to 6.2 (slightly acidic); this is suitable for most hydroponic crops. For soil,
we want the pH a little higher but still slightly acidic; around 6.0 to 6.5. Ensuring that the pH
remains within this range will help maintain good plant health. Keeping the pH in this range
ensures that nutrients are readily available to the plant. Once the grower goes above or below
this optimal range certain nutrients start becoming unavailable to the plant (e.g. iron
deficiencies will appear at a pH of 6.5 and above).

All hydroponic growers need to test the pH of their nutrient solution for successful growing. The
pH of a solution can be tested using a standard pH test kit (sample vial with drops of indicator
solution), litmus test strips, or a digital pH meter. Litmus paper and standard test kits are
cheap and easy to use; however, the degree of accuracy isn't very high. Digital pH meters,
although more expensive than the alternatives, are easy to use and very accurate.

4. Should I top-off my reservoir with plain water or nutrient solution?

In the summer or in hot grow rooms, plants, in general, will take up more water than nutrients,
thus causing the nutrient solution to become more salty. In the winter time or in cooler grow
rooms, the opposite will occur. Nutrient uptake will also be determined by the type of crop
being grown e.g., tomatoes are heavier feeders than lettuce. It is extremely important that the
grower has both a TDS meter and a pH meter and that regular testing on the nutrient solution
is carried out. If the grower notices after a few days that the ppm level in the reservoir is high
and the water level has decreased than the grower should top up their reservoir with either
plain water or a weak nutrient solution until the optimum ppm level is reached. If the grower
has noticed a drop in ppm levels then a full strength nutrient solution should be used to top off
the reservoir. Another factor to consider is the source water. You will generally find that if you
are not using reverse osmosis water, you will usually have to top-off with plain water, since tap
water has a lot of sodium and minerals that increase the ppm levels. Here is an ideal
scenario: Purchase a Reverse Osmosis System, Auto Shut-off Kit and some R.O. Tubing,
which can be found in the Water Treatment section of T he Barn's Back Door Store, and a ¼”
Grommet and a ¼” Float Valve, which can be found in the Plumbing section. Also purchase a
Rubbermaid trash can and a couple of cinder blocks from your local hardware store. Hook up
the R.O. system and shut-off kit according to the instruction manuals. The float valve that
comes with the shut-off kit should be installed in the trash can, which should be placed on the
cinder blocks for elevation. Drill a hole close to the bottom of the trash can and insert the
grommet. Install the second float valve in your reservoir, a little higher than where you want the
water level to be. Then, run a length of R.O. tubing from the grommet to the float valve. Now,
turn on your R.O. system and go spend the time you’re going to save doing something fun!
After a period of time, both the reservoir and the trash can will be full, and the R.O. system will
stop. It will only come on when the levels in either receptacle begin to fall. Once you add
nutrients and enhancers to the reservoir, you will find that the PPM level actually drops each day
as the plants take up nutrients and the water is replenished through the float valve (this is
especially visible with healthy, actively growing plants). You will also find that you use far less
pH adjusting solutions due to the improved water quality. You should only have to add small
amounts of nutrients and pH adjusting solution every once and a while between reservoir
changes. And, you will always have plenty of pure, fresh water available in the trash can.

5. What kind of maintenance is involved with a hydroponic system?

As with soil-based production, producing crops in hydroponic systems always requires
maintenance. The following list may seem like a lot of work; however, as you become
experienced most tasks and checks will only take a few minutes each day.

Daily

* Check reservoir for water levels, pH and TDS fluctuations.

* Check grow room temperatures and humidity percentages.

* If you use CO2, the CO2 system should be checked to ensure that it is working correctly.

* Check watering system. If a pump fails it should be replaced immediately. If drippers are
blocked they should be cleaned or replaced immediately.

* Check plants for disease and insect infestations. It is always best to stop disease and insect
outbreaks early. The longer an infestation is left the more difficult it will be to cure, yield losses
will be high and crop failures are possible.

* Check plants for leaf discoloration and deformities that may be caused by such problems as
nutrient deficiencies or nutrient burn (over feeding), as well as leaf curl from lights being to
close.

* Crop hygiene is extremely important. Cut off and discard diseased leaves. If a plant is badly
diseased, it is always better to throw out one or two plants to control disease outbreaks than it
is to destroy a complete crop. The same applies to insect infestations, especially spider mites.

* General maintenance - failed light bulbs, light movers, fans, loose ducting, leaks etc. should
be replaced or repaired.

Weekly

* The growing medium should be flushed once a week to stop nutrient lock up.

* Complete reservoir change should done weekly to prevent nutrient imbalances and bacteria
build-up.

* Foliar spraying for disease and insect pests should be done weekly to prevent outbreaks.

End of each crop

* The hydroponics system should be completely sanitized at the end of each crop. This will
minimize disease carry over to the next crop.

* The grow room should be sanitized with insecticides and fungicides. Walls, floors, ceilings
and equipment should be wiped down to remove insects/eggs and fungi spores. The cleaner
the grower is in his growing room the fewer problems he will have in the following crop.

6. Total Environmental Control

Too hot in your room – vent out your light. Too cold - add a heater. Too humid - bring in some
fresh air. Indoor gardening allows you to provide optimal conditions for your plants to grow in.
Being indoors also helps avoid mold, pests and other adverse creatures.

7. How often should you change your reservoir?

We recommend that you change your reservoir once a week. This entails “dumping” your
reservoir and re-filling it with fresh water and nutrients. The reason for this is that as the plants
feed, the nutrient solution will fall out of balance. Also, bacteria grows at a geometric rate. If you
change your solution every week you will decrease the possibility of bacteria becoming a
problem. While it is possible to go longer between changes if you are using reverse osmosis
water instead of tap water, you still have the bacteria issue to contend with, so unless you are
using something to inhibit the bacterial growth, you should still change your reservoir weekly.

8. What size water pump do I need for a reservoir that hold “x” number of gallons?

The size of your pump doesn’t depend on the size of your reservoir; rather it depends on how
far you need to pump your water and how much water you need to pump. You want to avoid
overworking your pump, so in choosing the proper pump you will want to choose one with at
least 20% more power than need. To find out your appropriate pump size you will need to
determine how much water is necessary to fill your tray. If your tray is in the shape of a
rectangle or square then you will need to apply the following formula to determine its volume:

Length (ft) x Width (ft) x Average Depth (ft) x 7.5 = ? US gallons

This will give you the total gallons that your tray can hold. It is a good idea to always get a pump
that is at least 20% larger than necessary to avoid overworking it.

After you’ve determined your volume requirements you need to find out how far “up” the water
needs to be lifted in order to reach the tray. Simply measure the distance between your pump
and the entry point in your tray; most systems will have a distance of under 3’. This vertical
distance will have an adverse affect on the pump and this affect must be accounted for. In
essence, the greater the vertical distance the water must travel, the stronger the pump needs
to be. The following chart will show you how vertical distance affects the pumps. Note the loss
of power of each pump as the vertical height increases.

9. What does an air stone do?

An air stone helps to provide oxygenate the nutrient solution. This oxygen is extremely
beneficial to the root zone and helps to promote fast, healthy growth as well as prevent
disease. This is one of the main reasons that plants growing in a hydroponic system grow so
much faster than plants in soil. If you are growing in soil you can still reap some of the rewards
of oxygen by simply oxygenating your water before applying it to the soil.

10. What is the difference between HPS and MH and fluorescent lights?
What kind of lighting do I need to grow plants?

There are two primary types of lighting used to grow plants. High Intensity Discharge (HID) is
by far the most common, and includes Metal Halide (MH), which is used primarily for the
vegetative stage of growth, and High Pressure Sodium (HPS), which is used during the
flowering or fruiting stage. You can find more information on HID lighting further down in this
FAQ section.

Another popular type of plant lighting is Fluorescent lighting. Fluorescent lighting is used
primarily for starting seedlings and cuttings, but T-5 fluorescent bulbs are strong enough to
grow short plants from start to finish. It is important to note that not all fluorescent lighting is the
same and only certain types should be used for growing plants. Most (if not all) standard
fluorescent tubes are fine for illuminating a garage or office, but usually lack the spectrum and
intensity needed to sustain plant growth. It should also be noted that if you are growing
houseplants that require very little light to sustain growth, you can probably get away with some
of the inferior types of fluorescent lights. But, if you are growing plants that need plenty of
natural sunlight in order to thrive (such as vegetables and flowers), you will be extremely
unhappy with the results you get from these bulbs.

There are three types of fluorescent bulbs that are considered suitable for plant growth:
Standard tubes with enhanced spectrum (such as the Verilux), Compact fluorescents and T-5
fluorescents.

Verilux

Verilux bulbs look similar to the bulbs you typically find in shop lights and offices. The main
difference is that, unlike standard tubes which lose their intensity and spectrum in as little as 6
weeks, Verilux tubes retain their properties much, much longer. They also have a spectrum that
is extremely close to natural sunlight. They can be used in any standard shop light fixture. They
should only be used for growing houseplants, orchids, or for starting seedlings or cuttings.

Compact Fluorescents

These bulbs are available in a variety of wattages ranging from 95W up to 200W. They produce
a higher lumen output than regular fluorescents, and are available in 6500K (daylight) for
vegetative growth and 3000K (red) to enhance flowering. Unlike regular fluorescents, compact
fluorescents do not require a fixture, since the ballast is built in to the base of the bulb. They
require a socket (the same type of socket you would use for an HID bulb) and a power cord,
and can be used with or without a reflector. Using a reflector, however, will direct more of the
light down onto the plants. Another common use for compact fluorescents is to hang them
vertically, usually without a reflector, in between large plants to provide supplemental side
lighting. Compact Fluorescents can be used for growing houseplants, orchids, or for starting
seedlings or cuttings. For plants that do not require full sunlight, or for varieties that tend not to
stretch under weaker light, these bulbs can be used for the entire vegetative stage, and in
some cases flowering as well.

T-5 Systems

T-5’s are the best fluorescent light bulbs available. They are similar to standard fluorescent
tubes, only much smaller in diameter. They put out far more light then standard fluorescents,
and have a much better spectrum as well. T-5’s must be used in a T-5 fixture; they will not work
with standard fixtures. They are available in different sizes and configurations, ranging from 2’
two bulb fixtures up to 4’ eight bulb fixtures. The eight bulb fixture is approximately equivalent to
a 600W HPS lighting system. T-5 bulbs are available in 6500K (daylight) for vegetative growth
and 3000K (red) to enhance flowering. T-5 systems are excellent for starting seedlings and
cuttings, and in many cases take plants from start to finish, provided you keep the plants on the
short side.

The rest of this lighting FAQ pertains mainly to HID lighting systems.

11. What size (wattage) lighting system do I need?
There are two things to consider when deciding what size lighting system to use: the actual
area in which the plants will be taking up, and how tall you want your plants to grow. 150-175
watt lights are primarily used for seedlings or cuttings, though they can be used for growing
plants to maturity if the plants are kept short. 250 watt systems are good for areas up to 2.5'
square at the most, as long as the plants don't get taller than about 2'. 400 watt systems cover
a primary area of about 3' x 3', or up to 4' x 4' max. 600 watt systems cover a primary area of
about 4' x 4', or up to 5' x 5' max. 1000 watt systems cover from 4' x 6' up to 5' x 7'. The taller you
plan to grow your plants, the higher the wattage needed. This is because the light intensity
diminishes by 50% for every foot you move away from the bulb. So, if your plants reach 4' tall,
then the leaves at the bottom of the plant are receiving only around 12% of the light that the top
of the plant is getting!

BALLASTS:
Magnetic ballast have been the standard for decades.

The Digital Ballast represents a breakthrough in HID lighting, and offer many benefits:

· Works with both MH and HPS bulbs

· Energy savings of up to 30%*

· Produces no heat

· No start-up spike of electricity

· Power factor (efficiency rating) is 99%

· Consistent wattage output - improves bulb life

· Components are American-made

· No stroboscopic (flickering) effect - as close to natural sunlight as you can get

· These ballasts also have a built-in safety feature. If an open circuit exists while trying to ignite
the lamp, the ballast will stop and then attempt to ignite the lamp again every 30 seconds for 2
minutes. The ballast will then go into a sleep mode for 30 minutes and then repeat. This saves
many dangerous and unnecessary attempts to ignite and burn out the ballast, which could
result in safety hazards.

REFLECTORS:

The reflector is undoubtedly the single most important factor to consider when choosing a
lighting system. The reflector dictates whether the light is concentrated on the plants, or
splashed up against the walls. While some bulbs are a little brighter than others, a quality
reflector can reflect up to 50% more light straight down onto the plants than a lower quality
reflector. Here’s a common mistake that first-time growers make. They see a reflector that is
advertised as covering up to an 8’ x 8’ area (with a 1000W bulb installed). Then they see
another reflector advertised as covering only a 4’ x 6’ area, and for more money, too! Which
would you choose? Well, consider this: Let’s say that a 1000W HPS bulb puts out 140,000
lumens (lumens is a measure of light intensity). Now, let’s say that you have a jar containing
140,000 marbles, each marble representing one lumen. You pour this jar into an area that
measures 8’ x 8’. You get a pretty thin layer of marbles. Now, pour this same jar into a 4’ x 6’
area, and you have a much thicker layer of marbles, right? Is it starting to make sense? Stay
away from the reflectors that throw the light all over the place, unless you are growing
houseplants! The smaller the area covered, the brighter it will be, and the better your plants will
grow and yield. Horizontal hoods are the best choice for plants that require a lot of light, such
as most vegetables & flowers. Horizontal hoods direct the light straight down on the plants,
throwing more intense light over a smaller area. This is by far the most popular choice among
growers. Air-cooled hoods have flanges that allow you to hook an exhaust fan to the hood to
suck out the hot air generated by the bulb, thus reducing the amount of heat in the grow room.

Urban Gardener offers the largest selection of reflectors anywhere, by leading manufacturers
such as P.L. Light Systems, Sunlight Supply, Hydrofarm, and, last but not least, Urban
Gardener.

You can find detailed information on all of the reflectors we currently carry in the Reflectors
category on our website.

BULBS:

How often do I need to replace my bulbs?

Urban Gardener recommends that HPS bulbs should be replaced at least every 12 months (8
months or less is ideal). MH bulbs should be replaced every 9 months (6 months or less is
ideal) for maximum efficiency. The use of a light meter would be the best and most accurate
way in which to measure your bulbs output as well as to help with bulb replacement timing.

What is the difference between an MH Regular and Super Bulb and how do I know which one I
need to buy?

A Metal Halide Super Bulb has a higher lumen (light) output, and is almost always position
oriented. These bulbs have a pin sticking out of the side of the mogul (base) where the bulb
screws into the socket. These bulbs require a position oriented socked that is designed to
catch the pin so that the bulb is rotated into the correct position, otherwise the bulb will not
perform as expected. In addition, these Super MH bulbs must be burned in a horizontal
position only. All other bulbs (non-position oriented), including the MH Regular bulb, can be
burned in either a horizontal or vertical position (i.e. they are universal) unless otherwise noted
in the individual bulb description.

GENERAL:

What is a recommend lighting schedule for Vegetation and Flowering?

For Clones/Seedlings and Vegetative Growth Urban Gardener recommends using an 18 hours
on/6 hours off lighting schedule. In order to induce your plants to flower we recommend
subjecting your plants to a 12 hours on/12 hours off lighting schedule.

12. Is it OK to leave my lights on 24 hours per day?

Urban Gardener does not recommend running lights 24 hours under any circumstances. Your
plants need a time to “rest” and grow. This is achieved during the dark period. Running your
lights for 24 hour cycles may have a detrimental affect on your lighting system and your plants,
not allowing them to develop properly. In addition, many plant species do most of their feeding
during the night, especially when daytime temperatures are high or humidity levels are low.

13. How do I determine how much my electric bill will increase by using a lighting system?

First, find out what your electricity provider is charging you per kilowatt hour (KWH). In Los
Angeles, it’s approximately $0.10/KWH, but this number will vary from city to city. This number
represents what a 1000W lighting system will cost you per hour to run. So, if you have a 400W
system, the number to use in the following steps would be 0.4, for a 600W system it would be .
06, and so on. Next, multiply this number by the number of hours per day you plan to operate
your lighting system. This will give you the cost per day. Finally, multiply this number by 30 to
see approximately what it will cost per month.

Refer to the following example:
0.10 (KWH cost for a 1000W lighting system) x 12 (hours per day) x 30 (days per month) =
$36.00 per month

Nutrients

14. How do I choose which nutrient to use?

There are many brands of nutrients that are available to hydroponic growers. The grower
should first decide if they want to grow organically or conventionally. The type of growing
medium will also determine what type of nutrient a grower should use, e.g. if coco growing
medium is used then you should consider using nutrients that are designed for coco (like
Canna Coco nutrients). The crop stage will also determine what nutrient should be used e.g. a
vegetative nutrient formula should be used when a plant is in vegetative stage (such as Super
Veg A and Super Veg B). Ultimately, the brand of nutrient which the hydroponic grower should
use is purely up to the grower to decide. And, as always, feel free to contact our sales staff and
we will be happy to make recommendations based on our own experience and the feedback
we get from our successful customers.

15. What is NPK, how does it affect my plants, and what combinations do I need?

N – Nitrogen

Nitrogen is a unique element, as plants are able to take up nitrogen in the form of an anion (a
negatively charged molecule) or a cation (a positively charged molecule). Plants are able to
take up nitrogen in as NO3 or Nitrates and NH4 Ammonium. Plants require or consume more
nitrates than ammonia, thus its not. A well balanced nutrient solution will have less than 10%
of available nitrogen in the form of ammonia. Nitrogen has many functions in the plant; it is
found in proteins, chlorophyll, protoplasm and plant hormones.

Source – All premixed nutrients will have adequate nitrogen levels. If a customer wishes to give
his plants extra nitrogen in the vegetative stage then he can use Cal-Mag Plus at a rate of 1-2
teaspoons (5-10ml) per gallon. This will supply the plant with 25 – 50ppm extra nitrogen, this
will be more than adequate. Using Cal-Mag will also supply the plant with extra Calcium,
Magnesium and Iron. If a customer wishes to use an organic source of nitrogen then they can
use Mexican Bat Guano. Note that only 1% of the 10% of nitrogen in Mexican Bat Guano is
readily available to the plant, the other 9% will slowly be released over a few weeks as the
organic nitrogen is broken down. Bat Guano cannot be used in NFT or aeroponic systems; it
will also have a limited affect in ebb and flow and drip systems. Bat Guano is ideal for soil
growers.

Deficiency – Growth is slow, sparse and spindly the older leaves turn yellow and will eventually
dry out and die. The complete leaf will turn yellow, with no green veins.

Toxicity – The plants will produce excess foliage that will be dark green. The plants will also be
softer, disease and insect outbreaks will be severe (this will be due to a weaker softer plant).
The root system will also be underdeveloped. High nitrogen levels can also retard flowering
and fruiting, decrease in yields as flowers don’t set and lower fruit quality. Nitrogen deficiency
and toxicity is rear and will not be a problem if growers use premixed nutrients and follow the
directions for these nutrients.

P – Phosphorus

Phosphorus is a very important nutrient for plants. It is required by seedlings, newly rooted
clones and flowering and fruiting plants. Phosphorus is essential for the development of
healthy roots, stimulation of flowering, ripening of fruits and seed production. Phosphorus is
also required for the hydrolysis of starch to sugar and for the synthesis of starch to sugars
(also known as energy transfer).

Source – Again, premix nutrients will have adequate phosphorus for general plant growth.
Plants will need extra phosphorus when the plants begin flowering and fruiting. This is why
growers must change from a vegetative formula to a flowering formula. The flowering formulas
will have higher phosphate and potassium levels to help stimulate flowering, fruiting and seed
production. This all culminates in higher yields and better tasting produce. Taste is increased
because of higher synthesis of starch in to plant sugars. For a customer to really boost their
yields of flowering and fruiting crops it is advisable for them to use a blooming enhancer.
Bloom Booster, Monster Bloom, KoolBloom and PK13/14 are all products that will boost
phosphorus and potassium levels. Bloom Blaster and Monster Bloom must be applied at a
rate of 1 teaspoon (5 grams) per 5 galloons of water. Kool Bloom ¼ teaspoon per gallon or 1¼
teaspoons per 5 gallons of water. PK13/14 must be applied at a rate of 1¼ teaspoons (5ml)
per gallon of water. For organic growers, in the soil, Jamaican Bat Guano can be used at a rate
of 2-3 (10-15 grams) tablespoons per gallon of water.

Deficiency – Plants are stunted and the leaves turn dark green to purplish color. This is due to
a buildup of Anthocyanin pigments. These symptoms occur in the older leaves first. Plant
maturity will also be delayed and yields will be low. Seed production is also severely affected.

Toxicity – Phosphorus toxicity is very difficult to diagnose. Excess phosphorus will cause
deficiencies of calcium, iron, copper and zinc. This will cause confusing signals as other
minerals may be showing signs of deficiencies even when adequate amounts of these
minerals are present.

K – Potassium

Potassium is the catalyst in plants. It is important for the manufacture and transport of plant
sugars/carbohydrates, increases the chlorophyll in leaves, regulates the opening and closing
of the leaf stomata and aids in disease resistance, water uptake and ripening process of fruits.
Potassium is also found in the juice of fruits which contributes to an increase of fruit taste and
fruit quality.

Sources – The sources of potassium are the same for Phosphorus above.

Deficiency – Symptoms occur in older leaves first with yellow blotches and in severe cases
dead spots will occur. Branches and stems will weaken and eventually becomes brittle.
Flowering and fruiting is diminished and yields are low and poor in quality.

Toxicity – leaf margins may burn in sever cases, but often it will effect the uptake of magnesium
and magnesium deficiencies will occur.

Ca – Calcium

Calcium is as important as N, P and K. Calcium is required in the roots, stems, leaves and
fruits of plants. It is found in every cell wall and is required for the absorption of nitrogen.

Sources – Most nutrient solutions will have adequate calcium for general plant growth. If a
customer is using RO water then they should consider using Cal-Mag Plus. An application rate
of 1-2 (5-10ml) teaspoons per gallon of water is sufficient to rectify any deficiencies.

Deficiency – Flower bud development is retarded, thus reducing yields, fruit size is decreased.
Roots die, leaving the plant open to root rot attack. Young leaves show symptoms before older
leaves. The leaves can be deformed, and have yellow blotches which later turns into dead
spots.

Toxicity – No visual symptoms; may cause magnesium deficiency.

Mg – Magnesium

Magnesium is found in the chlorophyll molecule. If a deficiency of magnesium occurs then
magnesium is transported from the lower leaves to the new leaves. Magnesium uptake is
affected by the concentration of Potassium. If high levels of potassium are applied then the
amount of magnesium should increase e.g. at the second week of flowering when blooming
enhancers are used then Cal-Mag Plus should be applied.

Sources – Most nutrient solutions will have adequate amounts of magnesium. If a grower is
using RO water then Cal-Mag Plus should be used.

Deficiency – Older leaves, lower half of the plants’ leaves show signs of yellowing. The
yellowing occurs between the leaf veins which remains green.

Toxicity – There are visual symptoms for magnesium toxicity.

Si – Silicon

Accumulates mostly in the epidermal cells of a plant. It is also found in other cell walls. Silicon
helps creates hardier, heavier and stronger plants. It has also been known to increase the
plants resistance to fungal attacks.

Sources – Silica Blast and Pro-Tekt (both potassium silicate) and Pyrosol are the main
sources of silicon. Growers should take care when using these products as they will increase
the pH of the nutrient solution, thus the grower will need to add pH Down to bring the pH back
to 6.

Deficiency – Deficiencies of silicon have been known to reduce yields.

Toxicity – Not known.

Why are some nutrients split into an “A” and “B” formulas?

Nutrients are split into two formulations because the phosphorus, calcium and sulfur nutrients
need to be separated from each other. If this is not done, then the calcium and phosphorus, as
well as the calcium and sulfur, in high concentrations, will react with each other to form calcium
phosphate (cement) and calcium sulfate (gypsum). Both calcium phosphate and calcium
sulfate precipitate out of solution, forming a white precipitate (which will usually fall to the
bottom of the reservoir), and are unavailable to the plants. This will cause phosphorus, calcium
and sulfur deficiencies in the plant. Once these nutrients are mixed together in the reservoir
they are at lower concentrations and also a pH balanced nutrient mix will prevent the three
nutrients from reacting with each other. This is another reason why balancing pH is extremely
important.

Some nutrients are one part such as FloraNova Grow and Bloom, are extremely thick and need
to be shaken well before mixing into the reservoir. If these nutrients aren’t shaken well before
use then the precipitates that have formed at the bottom of the bottle aren’t remixed into
solution. This will cause deficiencies, slow growth and reduced yields.

Some nutrients also come in three parts. This is done with some brands of hobby hydroponic
nutrient formulas so that the grower can mix the three parts in different ratios to create different
solutions for the vegetative and bloom stages, as well as for different types of plants, without
having to switch to a different product. Most commercial formulas, however, are two part (you’ll
never see a commercial hydroponic farm using a one or three part nutrient formula; they are
primarily for hobby growers).

Hydroponics