I recently needed a hospital tank and ended up using a plastic cake box from my kitchen. A 50 watt heater fit in there nicely. It was a fighter fish so it didn't need a filter luckilly. If it's another fish next time, I may buy a small hang on filter. I'm still not 100% sure about cycling. If I buy the hang on filter in advance, I may be able to squeeze some of the filter media from the new filter, into my current filter's casing. If not, I could squeeze my current filter sponge in a jug of tank water, then squeeze the muck into the new filter sponge.