I recently purchased a 120 gallon freshwater aquarium, along with about 50 fish. The fish tank was very dirty, and infested with smalll snails. I didn't get to save much of the aquarium water, as it was really dirty (Black sludge, at the bottom). I saved some of the original rock/gravel, but had to rinse it really well to get rid of all the snails. The only other thing I kept was the bio-wheels from the filter, which I floated in tank water. The tank is now set up in my home, what can I do to prevent fish loss due to this big move? I know it probably will go through a cycle again, as if it were a new tank!! Should I make small water changes if amonia starts to spike?