Depends, what are the tank dimensions. You want your fish to be able to turn around in the tank without having to bend their body. If the narrowest part of the tank is under 16 inches, i give him a years, maybe 2, and the O will outgrow it, and that is with very little decoration and maybe no tankmates.
These are dirty fish and sloppy eaters, and without the proper filtration and water changes they can foul the water quickly which when coupled with the stress of a small or overcrowded tank, and lead to disease.
The funny thing is that all of those water changes that you do to keep the water clean can also accelerate the O's growth. Hope this helps.