When I purchased a rehomed betta and his tank equipment, I ended up eventually replacing the heater and gravel (the heater wasn't enough to heat the tank size and the gravel was... tacky an fluro). Even now I'm considering just making my own sponge filter to replace the one that it came with- the suction on the tube holding the sponges for bacteria is weak or non-existent, yet the filter is somehow sucking water from somewhere else. The only thing that will definitely stay the same is the glass tank itself and the little half-log ornament he came with.