Raising fish, heater should be fixed securely, because some big fish tail could easily be bumped on the cylinder wall broken. Heater not buried in the sand or in direct contact with the glass. Once there are fish friendly because uneven heating barsdirect contact glass, lead glass is heated and cracked. Heater diagonal or flat, better cooling effect, even though it may not look good. Because heating the water is rising, so vertical GE's bar, rods of lower water with great temperature difference at the top of a relatively small, heat will slowly, which reduces the efficiency of heating, prolong the heating time, wasting energy. The clumsy like Rainbow fish, the bestheating rods and casing, preventing fish burns. If the cylinder has two heater, try them on both sides of the cylinder, uniform heating. And the thermometer should be kept where it is farthest from the heater, ensure the water temperature does notcome from just heat out of hot water.