10-Gallon Guidelines: Number of Fish, Heater Wattage, Filter GPH, Lighting

Ten-gallon fish tanks are many people's first aquarium because of their easy-to-manage size. Here are a few guidelines if you are considering purchasing one.

How Many Fish Can Live in a 10-Gallon Tank?

If you follow the typical rule of thumb (you can hold 1 inch of fish for every gallon of water), then you will be able to hold about 3 fish averaging 2 to 3 inches in length each in your 10-gallon aquarium. This is for freshwater. Minus a fish for saltwater.

What Size Heater Does a 10-Gallon Fish Tank Need?

A 10-gallon aquarium requires approximately 50 watts of heat. You would need either two, 25-watt heaters; or one, 50-watt heater.

What GPH Filter Should be Used in a 10-Gallon Aquarium?

A 10-gallon fish tank should have a filter that pushes at least 50 GPH (gallons per hour) of water through the filter. For saltwater roof tanks, the flow should be between 50-100 GPH of total water flow (between the return filter pump and powerheads or similar).

How Much Lighting Does a 10-Gallon Fish Tank Need?

A 10-gallon fish tank should have at least 5 watts of light (for a non-planted freshwater tank), on up to 50 watts of light for a full saltwater reef tank.

Please note this is for standard florescent bulbs, LED lights would require much less!

Also note that because of the relatively small quantity of water in a 10-gallon fish tank, you risk overheating the water if the light wattage is pushing the higher end of 50 watts. Use cooling methods as needed, including an open top with fan or a chiller.