Backyard Aquaponics
A place to discuss aquaponics

I'm building a new Aquaponics system and thinking about making my DWC bed as a partial flood and drain system.
I would pump the water from the FT to a media filled bed to filter it and then direct it to a DWC bed. The pump would be on a timer and would run long enough for both beds to fill and overfow through standpipes. When the pump shuts off, the water in the beds would then drain to the FT slowly through holes lower in the standpipes eventually achieving a complete drainage in the media bed and leaving a half full DWC. The plants are in mesh pots mounted in holes in a plywood cover on top of the DWC, not in floating rafts. The water level in the DWC would rise to the bottom of the mesh pots at flood and then about 6 inches lower at the drain cycle. There would remain about 5 inches of water in the DWC so some of the roots would always be submerged. The top part of the roots would be in the air and able to absorb oxygen during the drain cycle alleviating the need for a bubbler in the DWC.
It seems to me that there is an advantage in this system over the standard DWC with the better oxygen for the plants and perhaps better water circulation. Since the plants would always have some roots in the water it would be safe from a pump failure. Having the baskets immersed regularly in water would make starting seeds easier.
Does anyone see any possible problems with this approach? I wonder why I haven't seen this tried before.
The attached drawing shows the system.The standpipe in the media bed has hole(s) drilled at the base allowing a complete drainage of that bed. The standpipe in the DWC has hole(s) drilled halfway up leaving some water remaining in that bed. The pipe connecting the 2 beds has a standpipe in the DWC so that the water in the DWC does not drain out through the media bed.

The only thing I can think of at the moment is that you will have a huge water level change in the fish tank if you are going to both fill the gaps in the media, and half fill the complete DWC area..

Yup, only way of having this work is to have constant flood (cant use timer).

if you only drain 25% of the water from the dwc bed - where you place the hole on your standpipe - it would be pretty close to using a media bed..

Out of curiousity... what is the advantage of omitting the media from one of the beds and making it DWC?

Can you explain why constant flood is the only way?

For me the advantages are not having to deal with tons of gravel and to have another system to compare with my existing media bed, It seems from my research that DWC or NFT are preferred for growing lettuce. It might be easier to move the plants around and to harvest because the roots are not imbedded in media. I could possibly also raise prawns in the DWC bed.

Cool ideas!

You could still have a timer but have it filling a header tank so it then gravity flows through the pipes... A friend does strawberries hydro like that... rather then have a pump on constantly

I am thinking of doing a similar system and wondered how you are coming along?

I was also wondering why you had your system drain some of the water from the media beds back into the fish tank instead of having all the water go through the DWC bed?