We were given a 55 gallon tank from a friend who upgrade to a larger tank. We got it all setup and started to cycle it with 2 goldfish. A few days after we added 2 Bala sharks, 2 Angelfish, and 2 Gourami (1 gold and 1 opaline). The next day one of the Angelfish didn't make it. Took it back to the LFS where I got them along with a sample of the water to test. Water tested fine and he said possibly the other Angelfish attacked it. It's been about a week since and we haven't yet added any other fish. During the last few days the remaining Angelfish has been keeping to himself and not really swimming around the tank like the other fish. Usually it just hangs out in one of a few spots. I noticed tonight that the opaline colored Gourami is the one that is nipping at the Angelfish. This Gourami also chases around the gold Gourami, but that seems to be more of a playful manner. Any ideas on what I can do?