What Temperature Should a Fish Tank Be? A Chart by Species

What temperature should a fish tank be?

For a typical tropical community tank, Aqueon’s range is 75 to 80 °F (24 to 27 °C) 1. That covers a lot of fish, but not all of them. Goldfish are happiest cooler, bettas and angelfish warmer, and a few popular fish like danios and white clouds are fine at room temperature. So the first step is to find your fish on the chart, then pick a number inside its range.

Temperature chart by species

This guide covers freshwater fish only. Every number below comes from a published source, named in the table. Where a second source we’ve already used on the site gives a different range, it’s shown too.

Our species guides go deeper on each: neon tetra, guppy, goldfish, cherry shrimp, corydoras, betta and angelfish.

Why sources give different numbers

The neon tetra is a clean example. FishBase lists 68 to 79 °F, Seriously Fish lists 70 to 77 °F 5 6. We don’t know exactly how each source drew its line, but a wide range probably says more about what a fish can survive than about where it’s best kept. That part is our inference.

Our rule: stay inside the narrower range and aim for its middle. For a neon that means about 74 °F. For a betta, 78 °F is inside every range we found. Note the peppered cory: Seriously Fish puts it much warmer than FishBase does, so check which source you trust before pairing it with a cool-water fish.

What range can your fish share?

If you’re keeping more than one species, they need to overlap. This table is our own calculation: we took the FishBase ranges above (for the betta, FishBase’s 75–86 °F) and found the temperatures every species in the group can live in. It says nothing about whether the fish get along. For that, see our betta tank mates guide or the care guides.

If you use the University of Illinois range for the betta (76–81 °F), betta plus neon becomes 76–79 °F. If you use Seriously Fish’s range for the peppered cory instead, the two cory rows shift upward and the cool-water row disappears.

Two things stand out. Bettas and cool-water fish barely overlap, so a betta in a danio tank means one of them is uncomfortable. And the shared range of a “classic” tetra-guppy-danio community tank sits mostly below the 75 to 80 °F people often set by default.

How much does an exact temperature matter?

It depends on who you ask. Aquarium Science says the temperature of a tank matters much less than hobbyists think. Its author says most freshwater tropical fish live comfortably at normal home temperatures, 65 to 85 °F, and that temperature swings don’t hurt tropical fish 9. He calls the idea that fish need a perfectly steady temperature a myth.

Merck takes a more careful line. A heater is necessary for tropical fish, it says, and you should keep a separate thermometer in the tank, because holding the right range for your species is “critical to their health” 10.

We’d split the difference. Within a fish’s published range, a degree or two either way isn’t something to lose sleep over. The real problems are the extremes and fast changes, covered below. Our heater size guide has more on how stable a tank needs to be and where to put the thermometer.

When the tank runs too hot

Direct sunlight can warm the water. Merck says the warmer the water, the less oxygen it holds, and if it gets too warm, fish can suffocate. It also notes that floating plants shade the water and soften temperature changes 10.

Aquarium Science adds a behavior note: 82 °F (28 °C) “will induce mating behavior and aggression issues with most tropical fish”, while it prefers 74 °F (23 °C) for community tanks 9. That’s the author’s own experience, not a study, so weigh it accordingly.

If your thermometer reads above your fish’s range, here’s what we’d do, in order: move the tank out of direct sun, check the heater isn’t stuck on, and add surface movement so more oxygen gets in. Fish at the surface gasping is the warning sign; see our gasping at the surface guide.

When the tank runs too cold

Aquarium Science says some tropical fish die quickly below 60 °F (16 °C), and that “acceptable excursions” outside a fish’s range are for short periods, not permanent living 9. It cites a study in which a heating failure dropped the water to 57 °F (14 °C) and about 20 percent of three corydoras species died 9. It also warns that a big water change with very cold water can kill a whole tank 9.

Cold also slows the filter. Merck says beneficial bacteria work less well at lower temperatures, so cool tanks should hold fewer fish 10. Goldfish and other temperate-water fish do fine at room temperature, Merck adds 10.

If the heater has failed, warm the tank back up gradually, not all at once. Our heater guide cites Merck’s general rule of no more than 1 °F of change per hour. Use water at the same temperature as the tank for water changes. Our water change guide shows how.

Does temperature matter when cycling?

Yes: warmth speeds up the bacteria that make a tank safe. We cover how warm to go in our guide on how long a tank takes to cycle.

FAQ

Is 72 °F too cold for a tropical fish tank? It’s below Aqueon’s 75 to 80 °F for most tropical fish 1, but inside the range of many popular fish: neon tetras, guppies, zebra danios and peppered corydoras all include 72 °F in their FishBase ranges 4 5 8 12. Aquarium Science says tropical fish do well at normal home temperatures 9. It is too cold for a betta or an angelfish.

Is 80 °F too hot for a fish tank? Not for tropical fish in general: it’s the top of Aqueon’s range 1. It is too warm for goldfish, whose Aqueon range tops out at 74 °F 2, and for white clouds and zebra danios 8 11.

What temperature should a betta tank be? 76 to 81 °F, according to the University of Illinois vet clinic 3. That’s inside FishBase’s wider 75 to 86 °F as well 14. See our betta care guide.

Do goldfish need a heater? Merck says goldfish do fine at room temperature 10. Aqueon’s range for fancy goldfish is 68 to 74 °F, and for comets and shubunkins 60 to 70 °F 2, so if your room stays inside the range for your type, you probably don’t need one. A thermometer will tell you.

What temperature is best for a community tank? Look at the shared range table above. Don’t guess from the 75 to 80 °F default if your fish include cool-water species.

Do I need a thermometer if I have a heater? Yes. Merck says to keep a separate thermometer to monitor the water independently of the heater 10.