Guide
What temperature should an aquarium be
For most tropical aquarium fish the right temperature is 24–26 °C (75–79 °F). Stability matters more than the exact number: fish cope better with a steady 24 °C than with swings between 22 and 28 °C.
Temperature for popular fish and shrimp
Match the range to the species with the narrowest needs in your tank.
| Species | Temperature |
|---|---|
| Neon tetra | 22–26 °C (72–79 °F) |
| Guppy | 22–28 °C (72–82 °F) |
| Betta | 24–28 °C (75–82 °F) |
| Angelfish | 24–28 °C (75–82 °F) |
| Bronze corydoras | 22–26 °C (72–79 °F) |
| Discus | 28–30 °C (82–86 °F) |
| Neocaridina shrimp | 18–26 °C (64–79 °F) |
| Fancy goldfish | 18–22 °C (64–72 °F), no heater |
How much can the temperature swing
- up to about 1 °C a day: normal, e.g. from the light during the day,
- 2–3 °C within a few hours: stressful for fish and a common trigger of ich,
- water-change water: no more than 1–2 °C off the tank.
If you need to change the temperature on purpose, do it by 1–2 °C a day.
Too cold: choosing a heater
In a heated home a thermostatic heater of about 1 W per litre (about 4 W per US gallon) is usually enough, in a cold room about 1.5 W per litre. Place it where the water flows so the heat spreads evenly. A heater can fail in two ways: it stops heating, or its thermostat sticks on and overheats the tank. That is why an independent thermometer or alarm is worth having.
Too warm: what to do in a heatwave
- Close the curtains and keep the tank out of direct sun.
- Shorten the lighting period, as the light also warms the water.
- Open the lid and point a fan at the surface. Evaporation cools the water by 2–3 °C; top up what evaporates.
- Increase aeration: warm water holds less oxygen.
- Feed less. Don't put ice in the water: cool it gradually, e.g. with a sealed bottle of cool water.
How to watch the temperature automatically
Aquarium Monitor measures the temperature continuously and sends an alarm to your phone when it leaves your range. It also warns you earlier when the trend shows it is about to cross a limit, and separately when it changes too fast, e.g. when a heater fails.
Frequently asked questions
Does an aquarium need a heater?
Tropical fish do if the room sometimes drops below 23–24 °C (73–75 °F), e.g. at night or in winter. Goldfish and many shrimp do fine without one.
What temperature for a shrimp tank?
Neocaridina shrimp do well at 20–24 °C (68–75 °F). Warmer water speeds up breeding but shortens their life.
How fast can I raise the temperature?
By 1–2 °C a day. Faster changes stress fish.
Keep an eye on your tank from your phone
The app is free and ad-free. The monitor runs on your Raspberry Pi.