I have a 10 gallon aquarium and it has 4 fish now. I have no gravel (it doesn't matter to them). And the fish I have now I have had for 3 years. I have no clue what they are, but they have very long fins. Anyway when we clean mine, we take out the decorations, then we scoop the fish out with a fish net (never use your hands), after that I take the decorations and hand scrub with no soap, while i'm doing that my dad washes the fish tank out sid with water and a little scrubby pad (no soap) Then we put in about 5 inches of water (treated water). Then we place the decor back in, and last but not least we place the fish in one by one.