Backyard Aquaponics
A place to discuss aquaponics

Hi Everyone I was planning to do a raft type in growing lettuce but as I did more research i found out that I would need to add proper aeration to the water that might cause root rot to the lettuce, I was thinking that would it be possible to add an auto siphon to the container as to let the roots grow or would this be a problem or shock the plants? Basically the growbet could be empty or I could also add rocks to it.

sample image as follows:

the reason I asked is that I also have problems with ants and leaf miners, I would like to beleive that this is one reason to discourage them or drown them because I saw some eating my lettuce!!!

Thanks,

James

I have grown DWC using bubblers under each plant. A flood and drain DWC would be fine, but I would place pipes or what ever for the foam to rest on so that it does not drop down when the water leaves. The roots will get longer than you think. As long as the tank does not stay drained long enough for the roots to dry out it will be ok. At disney they have those plants that move on a conveyor. The roots just hang in the air and pass through a spray every few minuets.

There are a few things that an AP system needs that the normal flood and drain gravel beds provide which a DWC raft system doesn't provide in and of it's self.

The flood and drain gravel beds provide the Bio filter and they provide a solids filter. If you are going to do a raft system, you will need to have a separate bio-filter and solids filter before the raft bed. I'm sort of experimenting with a version of this but with NFT instead of raft. The water that comes out of one of my grow beds feeds a header tank that then slowly feeds my NFT tubes. You could do a version of this with a raft bed if you wanted. The biggest issue with DWC crossed with Aquaponics and the plant roots not getting enough aeration is probably due to solids building up around the roots and smothering them (the decomposition of solids can use up a lot of O2 causing dead zones in DWC) causing root rot. This is why systems that don't simply use flood and drain gravel beds, need separate solids filtration.

Jamesto,

I like the concept and think it should work, although I agree that you might want more supports for the foam. Only problem I see is volume: if one thinks having a sump to deal with the gb water volume is annoying, what will one make of a sump 3x that volume? Hmmmm..

Feasible.

I don't have hard facts and figures but I would suggest the fish would die from low oxygen before the lettuce. So supply enough O2 for the fish and the plants should be happy and no need to complicate the simple DWC system. You will require some sort of pre-filter / bacteria coloniser ,, whether that is a gravel type bed or a filter is up to you.