do you have fish in there?
if you do then take out all of the gravel and scrub and rinse til your hands hurt, i would also recommend using as hot a water as you can handle to clean the gravel
any other decorations do the same to, if the arent plastic boil then
as for the tank it self scrub hard and rinse out and clean well all filtering system pipes etc
and do a 75% water change
and add some melafix, to treat any possible fungul diseases


hope this helps

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i have 2 community tanks
and i breed angels and bristle noses

i love my fishies