I have almost the same set up except that I use a 39 gallon trash can from Lowes with a plastic faucet at the bottom to drain 1/3 of the water daily because I don't have a filter system at all. I refill it with RV filtered water directly from my home faucet and feed them jokers daily or they will start to eat each other. So far I have maintained @3 pounds for 6 to 8 weeks without any problem. I may loose one minnow every other day on average.