darkening roots on floating raft

[vihalvor]

Ok .. so i have my watertank cycling in anticipation of a growthbed for aquaponics... i.e so far its a standard floating raft HP system .. i have some Sweet Basil growing, but the roots, 1 week in after transplanting to the raft, are starting to lose its pristine white colour, and all going darker ....
The FIRST time i ever had HP salat, the roots where pristine white until i harvested them... not sure what im doing wrong... ?
too little nutrients in the water? ... cant be too little air, the raft is sitting on the airbubbles .....

please help...

-vidar-

[keith_r]

are you filtering the water before it goes into the raft tank? could be solids buildup which in turn can cause root rot

[Pugo]

just keep in mind that an air pump doesn't put oxygen into the water via the bubbles. It happens when the bubbles rise to the top of the water and break the surface. So if your raft is sitting on top there will be little oxygen in your system..

[vihalvor]

ooohh.. ok... so if i raise the raft just over the water lining... that should help a lot ? say.. if i have a 10 ,, styro raft... and i put enough styro under it, to raise it 5 cm ... just so the roots reach the water, but no more.... that should help, right ?

[Pugo]

Question what process are you using to cycle your system? Another question what nutrients are you giving your plants now? What is normally recommended is seaweed extract..

[vihalvor]

I have a new nutrient system, developed by UPLB .. worked like a LIGHTNING the first set of plants i gre .. but due to overbusy schedule i had to drop planting new ones ... so thats why im starting up again now.. more time on my hands, and REALLY wanting to get back into this .. :D

[vihalvor]

As of now this is a PURE HP system .. only the waterbed and a double aerator ... with the floating raft on top ...

[jobney]

Not that I think this is your issue but... Oxygen is attracted to water and wants to enter it at varying degrees based on how much oxygen is already there. This happens at the surface usually and it happens faster if there is more surface area. Turbulence from bubbles or rough current at the surface is one way to increase the amount of surface area. It's actually more accurate to say this happens at the air/water interface. Almost all commercial raft growers float the rafts directly on the surface. It seems to work just fine. UVI states that the raft bottoms, roots, and tank sides is the location of their nitrifying bacteria. The air bubbles do form pools of air under the rafts and the air / water interface should be great enough to get (some/adequate, not a lot of) o2 into the water then to the roots. The o2 also stops anaerobic bacteria from growing on the roots. The bubbles also circulate the water around the roots. One thing you'll notice about the UVI and other commercial systems is that not every plant site gets hit with bubbles. Friendly Aquaponics has this to say. A good read. http://hosted.verticalresponse.com/527375/990fe8f2ff/1451002247/851f16240b/ FA notes that the DO from the fish tank was adequate for short DWC troughs. Their bigger issue was lack of circulation around the roots on longer runs not the lack of DO.
I agree with keith_r. Suspended solids must be removed for DWC and NFT or the roots will do it for you and that's not a good thing.

[vihalvor]

theres no fish in this tank whatso ever.... im heading over to the pet store to get another air hose , as i have an unused air tap.. just to make sure theres as much air around as possible....
maybe i should just get the water pump too, place it on the SIDE of the tank, so it will circulate water...=?

-vidar-

[jobney]

Well that sucks then. Yeah without another tank flowing in with extra DO you may need to take a note from our weed growing friends and make it boil with air.

theres no fish in this tank whatso ever.... im heading over to the pet store to get another air hose , as i have an unused air tap.. just to make sure theres as much air around as possible....
maybe i should just get the water pump too, place it on the SIDE of the tank, so it will circulate water...=?

-vidar-

[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