I came home from a 6 day vacation and everything was fine in the aquarium on first check. I fed the fish and my largest male boseman was doing this weird shimmy. It looked like all he could move were his fins. His body had a slight curve to it, but the strange thing was he still had good color. He even ate a little. The next day he was still alive but more "frozen" and only flipped around on the bottom (burst of fin movement followed by slow assent to bottom). The curvature of his body was slightly worse. I came home from work and he was still alive but still in his sad state so I had to put him down. Also missing was a 2.5 inch albino briselmouth pleco. His tail was all that was left, the ghost shrimp had cleaned everything else. Here are the tank parameters: 78F, 30% wc 2 days before I left and there is nothing wrong with the other fish. The other fish include 16 cardinal tetras, 4 beckfordi (sp?) pencilfish, 5 remaining rainbows, and one otto and 10 ghost shrimp. I thought if water conditions were bad the shrimp would be the first to go, they are thriving however. The tank is 55 gallons with a 11 gallon sump/fuge. I am really puzzled by this. Before the vacation I gave them mostly frozen food to give them a little boost for the fast. Any suggestions?