I should have a fish tank that will be the equivalent of my grow bins to give the fish enough room and handle the exchange of nutrients efficiently. So far I have planned for a little more than 200 gallons worth of grow bins and planting tubes. The commercially available tanks take up too much room or are too expensive, or both. If I build a strong wooden box that is 2' x 2' by 8' it will have well over 200 gallons in capacity and it will fit neatly in my greenhouse. Fish pool liner and wood for the pool would come to under $100. Since I don't have to deal with outdoor conditions, cattle (as in a stock tank which is built to withstand large animals), or other similar conditions, it seems the best solution to my need for a large tank.
We installed the fish tank, plumbed the grow bins and decided to do a water test before adding gravel or chemicals. The grow bins each consist of three 27 gallon bins connected with ABS pipe with the bell syphon installed at one end of one of the bins. The sump is an old porcelain/cast iron bath tub. I have a 550 gph pump. The cycle went beautifully from the first in one set of bins and required only a little tweaking in the second set of bins to work as well. Meanwhile we were filling the fish tank. It had reached the point of beginning to drain when we heard a little popping noise then a wave of water ripped the side of the fish tank as over 200 gallons gushed across the greenhouse floor. It immersed the electrical cord connection but fortunately it was on a breaker and immediately cut out before we could be electrocuted.
We quickly discussed what could be done as the greenhouse slowly drained. We purchased concrete mix, chipboard for forms and reinforcing mesh. Today we will mend the side of the fish tank, create walls of concrete to contain what is now liner. None of the joints of the fish tank failed. It was a simple failure of the material. With concrete walls to provide the resistance to pressure we should be back in business again and ready to add gravel to our grow bins.