I upgraded from a 35 gallon tank to a 78 gallon tank, my new tank cycled fine and moved my fish over, 1 Bala shark (about 8 inches) 3 gourami's 3 tetras and 2 algae eaters. We recently bought 2 clown louches and added them. The first day they hid out but after a day were out swimming together. It's been a week and now I can't find them . I have sand in bottom and a few rocks with crevices, but no sign of them (no floaters) any suggestions?