I have 2 Blue Gouramis (3 spotted) and they hangout behind the filter. Why is that? They are not aggressive to my other fish (2 Dalmatian Mollies, 4 Assorted Platys, 2 Red Eyed Tetras, 3 Neon Tetras, and 2 Danios) , they are just the opposite, they are afraid to come out and swim around unless...