Location of Airstones
in the Hydroponic System

by Bob
(Fish and Jacks, Canada)

Hey Jason,
Thanks for the great website!!!!

I was reading over your page "My Most Successful Homemade Hydroponic System" and noticed in the drawing that it appears the aquarium pumps and air stones are inserted at the elbows. In the text you did not mention the location of the air stones.

I was wondering, if I had three air pumps and 6 air stones in the reservoir, would that do the trick? I elected to go a bit bigger with the design and went with 20 feet of 4 inch by 4 rows as in the drawing, giving me 96 plant holes.

Happy growing!

Answer: Bob- when I originally designed my most successful homemade hydroponic system, my concern was that the oxygen in the nutrient solution would be depleted as the solution flowed through the roots of more and more plants. I will be the first to admit my knowledge is limited, but this concern came from what I know about how oxygen affects plant growth.

If this assumption is correct, it made sense to me to space air stones throughout the hydroponic system to replenish the dissolved oxygen levels every few plants....this way the plants farther along in the system would not suffer for lack of oxygen.

To what degree my assumption is correct is debatable. On one hand, the rate of flow through this system is so quick that the plants may not have time to sufficiently deplete the dissolved oxygen before the nutrient solution is recycled through the nutrient reservoir. I believe this is probably the case with this system design.

On the other hand, most plants prefer a well drained root zone with a lot of air....having air stones every few plants could be the difference between having good results or bad results, especially if the plants are surviving close to the limits of their natural abilities in that environment. Also, as the number of plants in the hydroponic system increase, the chances of my assumption being correct also increase (which would be the case with your larger system design).

The air stones in my design are, indeed, installed in the elbows of the system. I made a 1/4 inch hole with a drill and inserted the air tube, then slid the air stone into place in the elbow and attached it to the air line. I found this strategy has one additional benefit... if your air stones are in the nutrient reservoir, they will be in the way when you go to do the nutrient change every two weeks.

Hopefully you have read my tip on using two nutrient reservoirs (one full of plain water waiting for the next nutrient change), which definitely makes life easier. It also eliminates the possibility of root damage from temperature shock. Also important to success is how to maintain the nutrient reservoir.

One more thing I must address before I let you go....hydroponic systems longer than 8 feet (of this design) have a tendency to sag in the middle. This is due to the weight of the water, and also because the plant holes weaken the structure of the PVC pipe. Even in my first 8 foot system I had a small issue with sagging because I had not provided any support in the center of the system. Therefor, my recommendation to you is to provide solid support points for the pipes every 4 feet.

I certainly hope my rambling ideas on this matter have helped. Once you are up and running, I would love to hear more about your final system design and what kind of results you are getting. Until than, Happy Growing!