You could, which would be interesting, make a double paned tank. Be a lot more work, but then it would still be viewable from all sides(Though few tanks are anyway) You could then also wrap it in polystyrene.
If you seal up the top of the tank(Double paned also) and have the only airflow going in going through hoses wrapped around your lighting's transformers that will decrease heat loss while recovering waste heat from the transformers. You'd need an outlet too, since the tank is airtight otherwise. You could make up a heat exchanger to preheat the air going to the transformers.
Make sure all your cannister filter's hoses and the filter itself are heavily insulated, that will stop heat loss and might be enough enough to recover some of the waste heat from the motor.
Put the tank near your refrigerator, cover the radiator coils in the back with more piping to extract heat from them. Done properly you have free heat for your tank AND your refrigerator would become more efficient.