°C
Temperature
What is it
Water temperature is the physical setting that controls the pace of aquarium life. Fish, plants, shrimp and filter bacteria all run their metabolism from the surrounding water, so each species has a practical comfort range rather than a single magic number.
Why it matters
Temperature changes oxygen demand, digestion, immune response and bacterial activity. Warmer water speeds biology up while holding less dissolved oxygen; cooler water slows feeding, growth and recovery.
Interactions with other parameters
Higher temperature lowers dissolved oxygen and makes CO2 leave the water faster. It also increases fish waste output and bacterial oxygen demand, so filtration and surface movement matter more in warm tanks.
Ideal ranges
| Tank type | Min | Max | Unit |
|---|---|---|---|
| Tropical community | 24 | 27 | °C |
| Planted high-tech | 23 | 26 | °C |
| Planted low-tech | 22 | 28 | °C |
| Shrimp tank | 20 | 24 | °C |
Out of range: what happens
Water that is too cold leaves tropical livestock lethargic and vulnerable to disease. Water that is too warm can cause gasping, higher ammonia pressure and rapid organic decay. Fast swings are often more dangerous than a stable value near the edge of the range.
Common Myths
- •Tropical fish always need very warm water; many live longer and breathe better at the cooler end of their range.
- •The heater dial is exact; most heaters need to be checked against an independent thermometer.
How to measure
Use a digital probe thermometer or a good glass thermometer placed away from the heater outlet. Adhesive strips on the outside glass are useful as a warning signal, but they are not accurate enough for decisions.
How to adjust
Raise temperature with a thermostatic heater sized for the tank volume and placed in good flow. Lower it with surface fans, better ventilation or a chiller; during heat waves, increase aeration because oxygen falls as temperature rises.
Pro Tips
For planted community tanks, a stable 23-25 °C often balances plant growth, oxygen and fish longevity.
In summer, aim a fan across the surface and top off evaporation with RO or demineralized water.
