staring with a gravity feed system

[Liz Tyner]

we are starting a gravity feed system and would like to know if anyone has tried this.  My Thought is to dump all the water from my fish tanks into a big media bed with worms and plants then gravity feed into a floating raft setup.  I am trying to eliminate the bafffle tank and the de-gas tank.  Has anyone tried this ?

[Jonathan Kadish NYC AA Chair]

I believe this is known as a 'hybrid system'. Search for that term on the forums and you will see that people are doing just that along with some other configurations that use the media bed for DWC & NFT filtration.

[Vlad Jovanovic]

At the forefront of this 'hybrid' discussion are sane stocking densities, percentage of media bed to raft ratios and to an extent, flow rates...This hybrid method is obviously working for some folks in certain scenarios. Their hasn't yet developed a 'cookie cutter' set of rules or anything...but you might want to consider...

1) At least a 30-35% media bed to raft - surface area ratio (assuming a 12" deep media bed is in question...I made mine a bit deeper...14"-16" for a bit of added filtration..)

2) Using the lowest fish stocking density that will still drive your system.

3) Design in, the possibility to add-on at a later time, should it become necessary a swirl filter...or at least something like Rob Nash's "polisher" (basically a bucket with some bird netting to catch the fines...after the media bed, but before the DWC trough)...

4) A good QUALITY fish feed that will leave behind less 'sludge'. Like maybe from Silver Cup/Skretting U.S.A

I don't know how big of a system you are talking about, but a de-gassing tank seems inappropriate and un-necessary in the above of scenario.

And I'd suggest lots and lots of reading and playing with Dr. Lennards calculator.

For NFT that Jonathan mentioned, personally I'd use additional filtration beyond just the media bed...Maybe from a "clean" sump. (aerated and somewhat mechanically filtered...)

[George]

a couple of examples

http://youtu.be/xKZhqnGJ1a8

http://community.theaquaponicsource.com/forum/topics/dwc-floating-r...

[George]

I like the idea of a polisher between the gravel bed and raft,   Not only will your raft water be clean but it should make your tank water nice and clear too.