I am setting up my hubby's 20 gal long from his pirrhana days as my quarantine/hospital system. I got a cheap Millenium filter and 40lbs of sand to put in it. I am planning on buying one or two medium rocks to put in there and a heater and I'm set. I am going to cycle it and leave it up and running all the time. I am going to put my talbot damsel (very docile and being picked on in my show tank) in there to maintain the biological element in the tank. Total, it has cost me about $75 to set the whole thing up, but I already had the tank.