Water Culture System

Convert an aquarium into a simple hydroponic system. The plants are suspended on a floating Styrofoam platform. This system is popular for classrooms because the roots of the plants are visible hanging below the floating platform.



AQUARIUM – Any water tight container with fairly vertical sides will work. Light breaks down the nutrient solution and encourages algae growth so if you us an aquarium you will need to construct a light shield out of cardboard or aluminum foil to keep light out of the reservoir (aquarium). If you wish to view the roots make the light shield (or part of it) removable.

FLOATING PLATFORM – You will need a piece of Styrofoam 1 1/2″ to 2″ thick. Cut Styrofoam to fit loosely inside the aquarium (or whatever you are using for a reservoir).

PLASTIC CUPS – Use several small plastic or Styrofoam cups to hold the plants on the floating platform. NOTE: We usually use Solo brand 3oz. plastic bathroom cups, but you can use any small plastic cup as long as it has tapered sides.

GROWING MEDIUM – You will need a small amount of growing medium, enough to fill the plastic cups. NOTE: The Professor recommends using Perlite or a perlite / Vermiculite mix for the growing medium.

AIR PUMP AND AIR STONE – You need to use an air pump and airstone to oxygenate the nutrient solution. A regular air pump designed for an aquarium is all that is required.

HYDROPONIC FERTILIZER * – A good quality hydroponic fertilizer is required, regular “dirt” fertilizers do not contain essential “micro-nutrients”. For more information about the differences in hydroponic and “dirt” fertilizers CLICK HERE.

pH TEST KIT * – You will need some way of checking and adjusting the pH of your nutrient solution.


  1. Cut the Styrofoam float to fit the reservoir. Cut the float a little smaller than the opening so that it won’t bind up when the water level changes.
  2. Cut the holes in the float to the proper size for the plastic cups that you are using, you want the bottoms of the cups to hang below the bottom of the float but not fall through. NOTE: We usually use Solo brand 3oz. plastic bathroom cups, these require a 1 7/8″ to 2″ hole.
  3. Cut several holes (aprox. 1/8″ to 1/4″ dia.) in the bottom of your plastic cups. Add growing medium to the cup. NOTE: if the growing medium falls out through the holes you can put a small piece of fiberglass window screen or small piece of cloth over the holes before adding the growing medium. For more information about Growing Mediums CLICK HERE


  1. Fill the aquarium (reservoir) with water. Mix your nutrient solution as per the instructions on the fertilizer package. Check pH and adjust accordingly. NOTE: The required pH value will vary depending on the requirements of the plant. For more information on pH, CLICK HERE
  2. Attach 1/4″ airline to the air stone and place air-stone in reservoir. Attach free end of tubing to air pump and plug in air pump to outlet, make sure that there are bubbles coming from the air stone. NOTE: NEVER submerge the air pump in water as electrical shock could occur.
  3. Place floating platform on top of the nutrient solution. Put plastic cups into the holes in the floating platform.
  4. When the plants have used up about half of the nutrient solution you can add WATER ONLY to bring the level back up (do not add fertilizer or you could cause a nutrient build up that could harm the plants). Recheck pH and adjust if necessary.
  5. When the plants have used half of the nutrient solution for the second time you need to change out the nutrient solution by draining the reservoir and then mix a fresh batch. Use the old nutrient solution on house plants or other vegetation.