We moved, I set up a 29 gal at the new house and moved fish along with power filter and sponge filter from the established 55 gal. To move the 55 we drained almost all the water but left the gravel in the tank. It sat in the basement for a week like that. Today I got it back online, the gravel had an earthy smell, not a rotten one like eggs. My question is since the gravel stayed wet and seems ok, will the tank cycle again? I will have my established power filter and the sponge filter and some driftwood to transfer from the temporary home in the 29. I don't want to risk losing my fish. Any suggestions on how to go about getting the 55 gallon back in shape (and good water conditions)??? I have rainbows which are supposedly very sensitive to poor water quality.