Best heater for a 90-gallon reef tank
The heater holds your tank at reef temperature. The right wattage depends on volume and — more than people expect — your room's ambient temperature.
Aim for ~1 W per litre — about 350 W total — for a 90-gallon (341 L) reef tank in a normal room. Size up for a cold room or a big day-night temperature swing.
Showing the 12 best-fit picks. 56 more heaters in the catalog — see all heaters.
Frequently asked
How many watts of heater for a 90-gallon reef tank?
Around 350 W (~1 W/L) as a baseline. Your room's ambient temperature matters more than the rule of thumb — a cold room needs more.
One heater or two?
Two slightly-undersized heaters on a separate controller (e.g. Inkbird) is the safe setup: if one sticks on, it can't cook the tank alone, and the controller is your failsafe against a heater's own thermostat failing.
Do I need a heater controller?
Strongly recommended. A stuck-on heater is one of the most common tank disasters — an external controller cuts power if the temperature climbs, independent of the heater's built-in thermostat.
Guidance only — sizing is a starting point; verify specs with the manufacturer before you buy.