Hydroponics: The Basics

Hydroponics means “working water.” If the medium itself does not contribute to the growth of the plant, and is only there as a structural support for the plant, then this is a hydroponic method. The water provides the nutrients and oxygen, doing all the work. Technically, if you are growing in coco or ProMix you are using a hydroponics method call Drain to Waste, which means you are not recovering and reusing the nutrient solution.

Hydroponics is not difficult, but does require more attention and more equipment. A power failure can be fatal in a couple of days for some methods, while soil is much more forgiving. Additives are immediately available to plants, and overfeeding can be easily corrected. Flushing is much easier. Production, when done properly, is enhanced. These are a few of the common methods.

Flood and Drain is the most recognized of the hydro methods. A large tray, fitted with an intake valve and an overflow valve, is set on top of a large reservoir. Rockwool blocks or net baskets filled with Rocks or hydroton provide the anchor for the plants. Set into the tray, a timer periodically floods the table when the pump in to res kicks on, and the overflow valve keeps the table from overflowing. When the timer turns off the pump, the nutrient solution drains back into the res. When the flooding occurs, the depleted air around the roots is forced out, and then fresh air is drawn down when the solution recedes. 15 minutes of flooding is good, usually 3 – 4 times a day. Watch your own plants though, and adjust accordingly. A 25 gallon res should be changed every 3 weeks or so. However, one sick plant will infect the entire tray.

Deep Water Culture (DWC) is inexpensive and easy. A net basket with grorocks or clay pellets, containing a rooted clone or seedling, is set into a bucket that is constantly aerated with air stones. The solution level is maintained at a high enough level to reach the roots. The level is lowered as roots grow and drop into the solution. You must change the solution weekly. There is little chance of cross-contamination with this method.

A Top Feed System, such as the WaterFarm buckets or the Dutch bucket setup sends solution, either through air pressure or a water pump, to a distributor on the surface. WaterFarms use a drip ring, and Dutch buckets use a dripper. Either way, the solution runs through the media and is collected and recirculated. Clogging of the drip ring or drippers, or the drain in a Dutch bucket, can be problems.

Slabs of rockwool can be placed in a tray, have nutrient solution pumped up from a res, and delivered to each plant in the slab through an emitter. Smaller blocks can be placed on top of the slab, or large blocks of rockwool can stand alone and use an emitter. This is timed so as not to oversaturate the blocks.

Aeroponics uses a spray system like a cloning machine. The difference is that the baskets containing the plants have a growing medium such as grostones or clay pellets. The sprayers run constantly, bathing the roots in a fine, highly oxygenated mist. Roots will clog the spray heads, as will nutrient buildup. The pump can raise the temperature of the nutrient solution to dangerous levels.

The Nutrient Film Technique (NFT) is very productive and VERY exacting. There has been a hybridization of NFT and aeroponics, but it is also very demanding and not recommended for anyone other than the expert grower who is obsessive/compulsive.

Growing media can be rockwool, grostones, clay pellets, or coco. The old school perlite+vermiculite combination is messy and not worth the trouble.

Grostones are actually made of glass, and provide a porous and sterile anchoring base for your plant’s stability and root development.

Clay pellets, such as Plant It! are small balls of clay that have been baked at such a high heat that they rapidly expand. The balls are porous and float until thoroughly saturated with solution. They provide a lot of airspace and are reusable. Use the same cleaning method as Rocks. These are easier to clean than grostones due to their regular shape. The pH is neutral.

Coco and Sunshine 4 drain fairly well, but should never be used in any method other than a flood and drain. Residue will still be a factor, and pumps will need frequent cleaning. Dispose of the remains. pH can be a problem. Sunshine 4 contains beneficial fungus.

Rockwool, made from cotton-candy like the spinning of melted basalt, is great for flood and drain or drain to waste. It is inexpensive and tried-and-true, but has a high pH that must be reduced to around 5.5. When the solution rises, used air is pushed out, and when the drain cycle occurs, fresh air is sucked into the rockwool. They are sterile, but will provide a growing surface for algae. This green slimy ick is not harmful to your plants, but it is a happy breeding ground for fungus gnats, whose larvae will eat your roots. Sprinkle coco fiber over the tops of the blocks, or use block covers to help prevent this. They are heavy and messy to discard.


Proper pH: pH (potential Hydrogen) controls the availability of ions the plant needs to assimilate nutrients. Since there is no buffer, as in soil, pH must be maintained between 5.8 and 6.4. pH ranges from 1 – 14, with 7 considered neutral. Battery acid is around a 1, and lye is about 14. Plants like a slightly more acidic (lower pH) solution. This is checked by drops or a pH meter. The drops change color when mixed with a small amount of nutrient solution, and the accompanying chart will tell you a reasonable approximation of the pH. A meter will give you an exact reading. The pH is adjusted with pH up and down, mixed into the solution in tiny amounts. A pen will give you a quick reading, while the drops can quickly become tedious. Also, some nutrients are colored, which can make distinguishing color tough. Buy the best pH pen you can afford. The cheapies usually require a new probe every six months. The glass ball that registers the pH on the tip of the pen must be kept clean and moist at all times. Weekly calibration of the pen will make sure your readings are accurate.

PPM, EC, TDS: These three scales are used to test the concentration of ANYTHING in pure water. Parts Per Million, Electrical Conductivity, and Total Dissolved Solids all measure this concentration.

Most tap water contains between 200 and 800 ppm of various things, such as chlorine, salts, and general crud. Well water is usually very high in dissolved calcium due to our limestone base. Your water needs to be cleaned before using in hydro. While soil can buffer some of these undesirable solids in solution, hydro does not have such a buffer.

PPM is the usual choice of measurement by indoor growers, and most pens are either ppm or TDS. EC is widely used in Europe. After cleaning your water, adding your nutrients, and pHing the solution, check for the strength of your solution. The reading should be reflected in your notes.

600 – 800 ppm = good veg numbers

900 – 1400 ppm = safe bloom

1500 – 1900ppm = experienced bloom

These numbers should be checked in your res at least every other day, or daily if you are changing your solution weekly, such as in a bubble bucked or WaterFarm. Sometimes the ppm will not change at all during the week; don’t laze out and let it go for another week. Check your plants for nutrient toxicity, and reduce the ppm of your next solution by ¼. If your plants are exhibiting serious signs of toxicity, use plain water only and check the ppms daily. You might find the ppms increasing; this means your plant is shedding excessive nutrients, and the original strength was too high. Some varieties are happiest with minimal nutrients; this is where your records can keep you from overfeeding next time.

FLUSHING: This is relatively easy in hydro. Flushing should be done at least twice in a full grow. Since successful indoor tomatoes are usuallydeterminate, which means all the fruit is ready at the same time, flush between grow to bloom cycle change, and then again a week to ten days before harvest.

Flushing involves preparing your pHed water with a flushing solution such as Final Flush or Clearex. Allow the mixture to run for 24 hours, and then dump the solution and either get on with the bloom cycle or for nearly finished crops give just plain water or water with a sugar, such as Bud Candy. Flushing will help remove the nutrients from your fruit, and replace them with sweetness. Synthetic nutrients tend to leave a metallic taste, and organics usually have a dirty or funky taste. Either way, if your plant has time to use up those nutrients, and replace them with good clean taste and aroma, your fruit will be noticeably superior.