What Size Heater Does a 55 Gallon Tank Need?

55 gallons sits on two Aqueon lines: 150 watts (30-55) and 200 watts (50-75).

Full breakdown: aquarium heater wattage guide.

Quick answer: A 55 gallon tank is the top of the Aqueon 150 watt band (30-55 gallons) and the bottom edge of the 200 watt band (50-75 gallons); the 100 watt band ends at 40 and the 300 watt band starts at 65, so neither includes 55. An angelfish minimum of about 53 US gallons fits in 55 gallons. A discus minimum of 67.37 US gallons does not.

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The figures

Figure	Value	Source
Question size	55 gallon tank	Aqueon
First band that contains 55 gallons	150 watts for 30-55 gallons	Aqueon
Second band that contains 55 gallons	200 watts for 50-75 gallons	Aqueon
100 watt band	15-40 gallons; 55 is above 40	Aqueon
300 watt band	65-90 gallons; 55 is below 65	Aqueon

How to size it

55 gallons is the other shared edge on the chart. Aqueon ends the 150 watt band at 55 and starts the 200 watt band at 50, so 55 is inside both.

30 ≤ 55 ≤ 55, so 150 watts includes it. 50 ≤ 55 ≤ 75, so 200 watts includes it.

The shared region is 50 through 55 gallons. A 55 is the last gallon of that overlap, the same way a 40 was the last gallon of the 100/150 overlap. The 100 watt band stopped at 40, and 55 is above 40. The 300 watt band starts at 65, and 55 is below 65. The chart does not say to add 150 and 200. The links below are a 150 watt heater and the next band up, 200 watts.

This tank is the first size in the heater set that clears the angelfish minimum. About 53 US gallons is under 55, and the angelfish temperature is 75-86°F. It does not clear discus. The discus volume is 255 liters. 255 ÷ 3.785 = 67.37 US gallons, and 67.37 is above 55. Oscar remains about 143 US gallons, also above 55. Dwarf gourami stays 56 ÷ 3.785 = 14.80 US gallons, with no temperature listed.

Species whose published minimum fits this tank

Angelfish joins the smaller species here, because about 53 US gallons is not above 55. Temperatures are species ranges. Dwarf gourami has no listed temperature.

Species	Published minimum	Temperature	Source
Betta (Betta splendens)	about 11 US gallons	72-86°F	Seriously Fish
Neon tetra (Paracheirodon innesi)	about 14 US gallons	70-77°F	Seriously Fish
Guppy (Poecilia reticulata)	about 11 US gallons	63-82°F	Seriously Fish
Zebra danio (Danio rerio)	about 21 US gallons	64-77°F	Seriously Fish
Bronze cory (Corydoras aeneus)	about 19 US gallons	70-81°F	Seriously Fish
Platy (Xiphophorus maculatus)	about 14 US gallons	68-79°F	Seriously Fish
Molly (Poecilia sphenops)	about 21 US gallons	70-82°F	Seriously Fish
Bristlenose pleco (Ancistrus sp.)	about 19 US gallons	77-86°F	Seriously Fish
German blue ram (Mikrogeophagus ramirezi)	about 14 US gallons	81-86°F	Seriously Fish
Dwarf gourami (Trichogaster lalius)	56 liters = 14.80 US gallons	Not listed	Seriously Fish
Cherry barb (Puntius titteya)	about 14 US gallons	68-81°F	Seriously Fish
Harlequin rasbora (Trigonostigma heteromorpha)	about 14 US gallons	70-82°F	Seriously Fish
Angelfish (Pterophyllum scalare)	about 53 US gallons	75-86°F	Seriously Fish

Still above a 55 gallon tank:

Species	Published minimum	Temperature	Source
Discus (Symphysodon aequifasciatus)	255 liters = 67.37 US gallons	Not listed	Seriously Fish
Oscar (Astronotus ocellatus)	about 143 US gallons	68-82°F	Seriously Fish

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Accessory: a digital thermometer for a tank that the chart lists at two wattages. Shop a digital aquarium thermometer on Amazon

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