The following information is provided for anyone new to hydroponics, or those interested in a different method of growing. Most of the information is based on many years of experience in hobby hydroponic growing. The methods shown are not necessary the best or the only way to grow, but have been proven to be successful in actual practice.
After one aquires a hydroponic system of some type, the question arises "Where do I start?"
Without doubt, the most important aspect of a hydroponic system is a good water supply. For those lucky enough to have a water supply that has little or no carbonates and other dissolved solids that plants cannot use have half of the battle won. Those on a municipal water supply can usually grow without too many problems.
Carbonates cause the PH to rise, which if excessive must be controlled.
Other dissolved solids that are not used by the plants will build up to a point where the nutrient must be changed or the plants will suffer.
The frequency of changing nutrient depends on the amount of dissolved solids and the amount of water that must be added over a given period. When the amount of water added is equil to the original, the unusable elements in the tank will have doubled. For those with good water and a meter to measure nutrient strength, there is usually never a need to change nutrient.
MEASURING and CONTROLLING PH
There are several methods of measuring PH. There are kits sold where one adds so many drops of a liquid to a sample of water, then a color scale will give the approximately PH. There is litmus paper that when dipped into the nutrient will change color depending on the PH. There are meters that measure PH, which are by far the most expensive method of measurement.
As a rule of thumb, if one can keep the Ph between 5 and 7, very few if any PH problems will arise.
If the PH is running too high, your plants will be the first to tell you.
The effect of high PH is the inability of the plant to pick up minor elements, with iron being the first to show up. An iron deficiency shows as pale yellowing young leaves with the ribs in the leaf looking normal.
A brief note about identifying minor element deficiencies: It is very difficult to identify precisely what element is deficient. This author from experience, adds a broad spectrum of chleated minor elements when any deficiency shows itself. In most cases, it solves the problem.
This addition of chelated minor elements will sometimes compensate for a slightly higher than normal PH when the plants show a minor element deficiency.
If one has a high amount of carbonates in the water supply, the control of PH is probably necessary.
The addition of acid is the only way to control high PH. This is where it gets tricky. It is highly recommended that anyone who plans to use acids to control PH review the rules for handling acids.
The two best acids to add are nitric and phosphoric. The danger of using nitric acid cannot be over emphisize.
No one should ever attempt to use nitric acid unless he/she has a great deal of experience with acids. Nitric acid is most unforgiving if it accidently makes contact with eyes or skin, or the fumes are breathed.
With all that said, if one has water very high in carbonates and the proper acid handling experience, nitric acid is the best way to go.
Phosphoric acid is the next best choice. It is not as dangerous as nitric, but it is still a strong acid and should be handled with caution as all strong acids should. I read another url posting that there is a reasonable priced source for phosphoric acid. It was listed as a dairy equipment cleaning acid called Monarch CIP acid, which is available at farm stores. I have never seen this product and know nothing about it, but it might be worth while for someone who is interested to check it out. If you decide to try the product, read the label carefully and be certain that there isn't any chemical that might be harmfull to plants or people.
Two other acids that are occasionally used by some individuals, mostly due to their availability rather than their desireability are Sulfuric acid (battery acid) and hydrochloric acid (used in swimming pools).
These are both strong acids and are dangerous if mishandled.
The undesireable aspects of these acids in a hydroponic system are the addition of chlorides and sulfides to the nutrient. Both can be toxic to plants if concentrations are high enough.
Another source of PH control is called PH UP and PH DOWN. These are basically weak solutions of acids or alkalines that are sold by hydroponic shops. Most are expensive to purchase.
There are a number of household acids that have been used. These include aspirin, vinegar(acetic acid), and citric acid. It is quite possible that if one of these acids cured a high PH problem that the problem was not that serious to begin with.
With some water sources, low PH can be a problem. Although not near as common as high PH, it could be a problem that must be dealt with.
The best compound for low PH is potassium hydroxide, but like nitric acid, it is a very dangerous chemical to handle. It is similar to lye(sodium hydroxide). If it is known for sure that low PH is causing a problem, one might try adding a small amount of baking soda. This would be adding sodium to the nutrient, which might cause a problem if too much is used.
This might be an unorthodox approach, but at least it is safe.
Two other solutions to bad water are bottled water and a reverse osmosis filtering system. Either of these methods can be very expensive.
MEDIUM
Several types of systems use a medium to anchor the roots. There a number of things that can be used successfully as medium. Expanded clay balls sold in hydroponic stores under a variety of names can be used, although they can be expensive. There is an expanded clay called Arcillite that is used in concrete and as a soil suppliment that can also be used. If weight is no problem, pea gravel or coarse sand will work well. Ground pine bark or most any type of wood chips used as mulch will do the job. Sawdust works good. Ground coconut husks are also used. Perlite and vermiculite work well, although vermiculite is quite wet for some plants. There are probably many more that could be used.
FERTILIZER FOR NUTRIENT SOLUTION
One of the questions that comes up for new hydroponic growers is what to use for fertilizer. A fertilizer that is designed for use in soil is usually not suited for hydroponics, although some can be used.
A fertilizer must be water soluable and contain minor elements in order to be usuable in hydroponics.
The nitrogen source is important. There is some controversy about using Urea nitrogen found in soil use fertilizer, but the general belief is that it will not work in hydroponics. Ammonium nitrate can be used in small amounts. Too much will cause root problems that can result in plant death.
Potassium nitrate, and calcium nitrate are the best forms for hydroponic growing.
There are three choices for fertilizer.
1. Use commercial hydroponic fertilizers. Advantage--excellent quality and reasonable cost. Disadvantage--difficult to find and comes in 25 lb bags and must be used with calcium nitrate which comes in 50 lb bags. Peters Hydrosol 5-11-26 is a good hydroponic fertilizer, but often difficult to find.
For those who live in Florida or North Carolina, Southern Agriculture carries a 5-11-26 hydroponic fertilizer at a very reasonable cost. http://www.southernag.com/
Another source for a good quality fertilizer is at TotalGro-SDT Industries, P.O. Box 805, 214 Fair Avenue, Winnsboro, LA 71295.
Another reasonable source for hydro fertilizer can be found at http://www.hydro-gardens.com.
Pro-Sol at http://www.4prosol.com/hydroponic.html Good quality and reasonable cost for South and South-West
Calcium nitrate is sold at most commercial nursery supply stores. (Note)Greenhouse grade calcium nitrate is easier to dissolve than field grade.
2. Speciality fertilizers from hydroponic shops. Advantage--good quality, many come in liquid form, and are available almost anywhere.
Disadvantage--expensive.
3. A water soluable fertilizer with minor elements that is as close to hydroponic fertilizer as you can find. None will be perfect, and will always have something in them that is not ideal, but many will work and produce decent plant growth. Advantage--reasonable cost and good availability. Disadvantage--All have something in them that is not ideal for hydroponics. Miracle Gro is probably the most used in this catagory.
If you are using a hydroponic fertilizer that has directions for use, by all means follow those directions, but most fertilizers do not have directions.
If you use a commercial hydroponic fertilizer or a near substitute not designed for hydroponics, you can probably get by using 3/4 to 1 tea spoon of basic fertilizer with 1/4th teaspoon each of calcium nitrate and epson salts(magnesium sulfate)per gallon of water. This will result in an EC of approximately 1.4 to 2.0
There are lists showing the optimum level of fertilizer for each different plant. Example: lettuce likes 0.8 to 1.2 EC while peppers like 1.8 to 2.2 EC. This does not mean that the plant will not grow at levels above or below those recommended. Those numbers are ideal, but plants are very versitle in that they will often grow under near adverse conditions.
If one is trying to make a living growing hydroponic vegetables, those numbers are important, but if one is a backyard gardner growing vegetables for his own table, use the numbers as a guide only. It probably would not be the best idea to mix lettuce that perfers 0.8 EC with tomatoes with an Ec of 3.0 or 4.0.
Most plants will grow reasonably well with the amount of fertilizer recommended above, with the exception of tomatoes.
The above amount is fine until the tomatoes begin setting on the plant,
then double or triple the amount of everything. In order to avoid blossom end rot, tomatoes need a lot of calcium, so increase the calcium nitrate. In order to produce high sugar contents in tomatoes, the EC must be above 2.5. Tomatoes are very salt tolerant and are seldom ever bothered by high nutrient concentrations.
THE TRUTH ABOUT TDS, PPM and EC
There is a lot of confusion about TDS, PPM and EC among hobby hydroponic growers in North America.
Hydroponic nutrient is made up of several different salts. Example:Calcium nitrate is a salt as is each of the other components that make up the fertilizer added to water to make nutrient. Salts in water conduct electricity, although each salt conducts at a different rate.
EC (electro-conductivity) is the measurement of current flow through a nutrient mixture. Total current flow through the nutrient is the only measurement of fertilizer concentration that can be taken with a meter. The greater the amount of fertilizer in the nutrient, the greater the current flow. The current flow is measured in milliSeimans per centimeter. This means little to the average hobby grower, but what does have meaning is the fact that most vegetables grow best within a range of 0.8 to 3.0 EC. Each vegetable has it's own ideal EC range for optimum growth.
TDS (total dissolved solids) and PPM (parts per million) are the result of a mathmatical computation. It is based on 1 milligram per liter of water = 1 PPM. If one weighs the fertilizer and measures the water accurately, the total disolved solids in PPM can be calculated. These numbers remain valid until the nutrient is made available to plants. It is impossible to measure the PPM of the nutrient in an active hydroponic system with any kind of meter.
The confusion comes from companies in North America making meters that measured current flow, but instead of using EC as the scale, they used a PPM scale, which was nothing more than a wild guess at what a normal mixture of hydroponic fertilizers would be equil to at any given EC.
To make matters more confusing, different companys used different numbers in converting from EC to PPM. Some used 550 PPM per EC while others used 700.
If you have a meter that reads in PPM, when you dip it into an active hydroponic system, you are getting a reading that is a wild guess as to what the PPM might be.
EC is the only accurate measurement of fertilizer concentration that can be taken with a meter in an active hydroponic system.
The question will eventually come up: Should I purchase a meter to measure nutrient strength?
The purchase of a meter to measure nutrient strength might be the most expensive item in a hydroponic system. The cost usually falls into the $75 to $100 range. It is one of those things that is nice to have, but not absolutely necessary. Without the use of a meter, the changing of nutrient periodically is advisable. One possible rule of thumb is to change the nutrient when you have replaced two times the water held in your tank. In other words: if you have a 20 gallon tank and the water level drops to 10 gallon, replace the 10 gallons with the same amount fertilizer per gallon as the original unless you are growing under hot conditions. Use about 1/4th to 1/2 the amount of original fertilizer when replacing under hot conditions. The 4th time this is done, 40 gallons have been added. At this time when the nutrient drops to a low level, dump it and start over as in the beginning. In many places, the quality of the water is such that it is necessary to change it anyway. Under these conditions it is difficult to justify $100 for a meter.
Not to be overlooked when guessing about changing nutrient is the condition of the plants. If the plants are looking good and growing normal, chances are that the nutrient is within the tolerance limits for those plants.
On the other hand if you have excellent water and are growing a lot of vegetables, a meter will give you control of nutrient strengths, and probably allow you to go an entire crop cycle without changing the nutrient.
When water, sunlight and nutrients are all present, a small microscopic plant called Algae will grow. Like most other plants, it is generally green in color. It can be very upsetting to a new grower to see this this green stuff growing on the surface of his/her medium, or inside the nutrient tank, or inside the nutrient feed lines. Algae is harmless to plants and unless it interfers with nutrient flow the worst thing about it that it looks bad.
Algae can be stopped very easy by preventing sunlight from hitting the nutrient. Using a material that does not allow light to enter the nutrient tank or feed lines eliminates most of the problem areas. Black tubing and dark colored tanks or painted with dark paint is usually the simplest way. If the Algae does not restrict nutrient flow, it can be ignored.
SEEDS
There are seeds that are specially bred for hydroponic growing, but as a hobby grower, common garden seed are just as good or better, because commercial seeds often are bred for amount of production and looks at the expense of taste. Whatever tomato taste best to you when grown in soil will grow as good or better in hydroponics.
PUMPS
One last item: purchasing pumps. There is no doubt that on line aquarium supply stores are the most econimical source for pumps. This author uses both Rio 600 and maxi-jet 750 pumps, but I am sure there are others just as good. Both work well, but the Rio in usually slightly cheaper to purchase. I did a quick search of the internet in Jan., 2003 and found these places that have reasonably priced Rio 600 pumps. http://www.aquadirect.com $12.89 http://www.aquatictech.com/pumps.html $11.99
http://www.premiumaquatics.com/pricetab.html $13.95 I have never done business with any of these companys, but they appear to be valid sites. I did not compare shipping prices. If one has time, a thorough search might find a better store with better prices.