darkening roots on floating raft

[vihalvor]

yah... will get another airstone and air line, along with the pump ...

[Pugo]

Whatever this is, It's an indication that some component of your system isn't working optimally. However it is possible that the color of the nutrient solution will stain the roots, turning them yellow or brown.
From what I understand being deficient in oxygen at the root zone is the leading cause of root death in Hydroponics. Are your trays tilted and supported to drain completely? Another problem can be too many plants competing for too little oxygen. These problems are worsened by high root zone temperatures. As the warmer the water the lower the DO (dissolved oxygen).

Your nutrient reservoirs should always be aerated by an air pump and air stone. You can never have too much oxygen, the more the better the way I see it. My knowledge is limited to basic Aquaponics and Hydroponics is way out side of my realm.

[vihalvor]

yah.. getting more air stones tomorrow... also lifted the whole thing so that the float is floating on small "islands" of extra styro "bricks" .. this give the float a claring of about 1/" inch .. lots of space for the roots... should help ...

[Pugo]

Here is a link Hydroponics videos that are how to with lots of useful information.. watch them I am sure your questions will be answered..

http://www.youtube.com/user/SureToGrowers