technically yes..but I wouldnt..
it would make a lousy aquarium..
because there is no where to hang a filter, and wires for a heater would have to run through the hole in the top..
also, cleaning it would be almost impossible, without dumping out the whole tank.
it would make an ok short term hospital or quarantine tank..
an air hose for a sponge filter could go through the hole in the top,
no gravel, and you could just dangle a heater down through the hole as well..
but for a regular, long-term aquarium..its really no good..
it would be very inconveient, and probably not very healthy for the fish..
its actually NOT an aquarium..its not meant to be one..
its designed to replenish water in an actual aquarium..
its not well equipped to actually hold fish.
Scot