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Comment by Courtney Edwards on December 16, 2011 at 11:29am

My latest and greatest system. I was interested in over-wintering a system in my less-than-skookum greenhouse.  

A 50 gallon barrel for a fish tank, wrapped in a water heater blanket and set on some dense foam. And a loose insulating cover for the top. There's 2 airstones in the tank. There's about 15 comets, 1 koi and a shebunkin (both rescued from a bathtub found out in a horse field when we moved in). Water then gravity feeds through 2" pipe to my old gravel grow bed. Where it floods and drains through a 1" bell syphon into my deep water trough. The gravel bed is now insulated with a blue camping foamie. The DWC trough is made out of 3/4" plywood that was epoxied together, with an EPDM pond liner (it's 2' wide x 6' long). It has rigid foam insulation on the bottom (in the trough, but outside the liner) and on the outside walls as well. Net pots with hydroton, little sticks to deal with the wrong hole-saw size and living in a small town that doesn't always stock what you need in the stores, and 2 airstones in the trough.  From the DWC it gets pumped from the end farthest from the fish tank back to the fish where it starts all over again. There is a sump dug into the ground just in front of the fish tank. The original design had the water draining into there where it would get pumped to the fish, but the ground is so cold that it was making it hard to keep the water up to temperature. I run a tiny fountain pump (head: 4 ft, 158 gph) and probably need to either get a bigger one or put two in a series because when my pump gets clogged there isn't enough water to trip my siphon. I have one small heater in the fish tank that is able to keep the system at about 18 degrees celsius (only because of all the insulation). I know I'm breaking all sorts of tank volume to grow bed volume ratio rules, but it's working great so I'm not too worried. There have been plenty of days where I go in to feed my fish and the whole greenhouse is a sheet of ice, the door is frozen shut, and my fish don't even know it's winter. The plants aren't doing much since I live on the north side of a montain on cloudy vancouver island, but my water quality levels are always acceptable. My next thoughts are to build a filter between the gravel bed and trough, and I am considering getting a grow light (I'm not know for my patience).