My background is that I am currently a market farmer and at one point in my life I was running a fish breeding system in my barn. I still have all the aquarium equipment but largest tank is 55 gallons. So the cycle, pH etc are old news to me. I fell and broke my back at work yet still lost everything including the ex wife. With her getting over half of my settlement and child support it has been a very long time recovering to a point I want to try getting back into the fish industry. I farm the family farm that is forty miles away but the house is close to half way between farm and markets so it works out that I am there 3-5 days a week depending on the season. Goal is to build a smaller system here at the house and then put up the full size green house at the farm for a larger system with auto feeders and extra pumps with battery back up once I am comfortable with this new adventure. A small green house of 10 X 11.5 ft is in the back yard. Plan is to have 2 IBC totes as the tanks with gravel beds for filtration then a seasonal DWC outside the green house with hoops of PVC to make the season longer. The type of fish is Koi for tanks and sailfin mollies for mosquito control in DWC with a possible crayfish species in my sump. Plan is for CHIFT PIST (constant height in fish tank pump in sump tank for those new to this). I have been reading about this adventure off and on for a couple years. I have been searching the net hard for the last few weeks as I am drawing out my design. I have several large pumps that need to be tested as they were used in the fish room 15 years ago.

Problems: Cash flow is very limited. I need help from those that scrounge up the items needed to build these systems. The gravel beds are going to be 10 3/4 inches high as that is two 2x6 high minus the plywood bottom, width is three feet, length will be determined by IBC size. I am hoping to use the shorter side of IBC along the longer wall. But the size is on the outside as I had to stay under 120sqf because of codes. Green house is built but not covered and plastic is waiting to be used. I started this project last year but markets are a summer thing and cash dried up.

My questions are can you get away with just using 6 mil green house plastic for the liner of the beds?  Can DWC beds be shallow like 6 1/2 inches ( 7 1/2 sides but with one inch foam in bottom)? Plan is for the gravel beds to be long term herbs like basil, rosemary, etc. The worry is with the gravel. I have made "ponds" out of green house plastic in the past for rearing fish outside with good luck. One was used for three years in a row. So I plan on using it for the DWC bed. Sump will be in ground just inside the green house so the DWC can be disconnected in cold weather. Green house will only be heated to 45 degrees until time to start seedlings.

Thanks for the advice ahead of time. John