Freshwater fish?considered?

TROPICAL MEANS THEY CAME FROM A TROPICAL TEMPERATURE AREA , AS OPPOSED TO SAY CATCHING SMALL FISH IN YOUR LOCAL AREA WHICH HAVE COLD WINTERS . YOU CAN HAVE A FEW SMALL BLUE GILL FRY IN A TANK SITTING BY A A/C DUCT WITH-OUT A HEATER AND THEY DO JUST FINE ----BUT SOME TROPICALS WOULD DIE IN THESE LOW TEMPS.