Temperature
Temperature influences every biological process in the aquarium: metabolism, dissolved oxygen, bacterial activity, growth of corals and plants.
Detailed explanation
Temperature is the most intuitive but also the most underestimated parameter. It's not enough to have a heater and forget about it. Thermal fluctuations stress organisms more than cold or heat itself.
In marine reef aquariums the ideal temperature is between 24 and 27 degrees. Above 28 the corals begin to suffer. Above 30 they expel the zooxanthellae and fade (thermal bleaching). Global warming is causing this phenomenon on a planetary scale. In the aquarium we cause it with heating pumps, powerful lighting, non-air conditioned rooms in summer.
Cooling is often overlooked. An aquarium fan lowers 2-3 degrees evaporation but increases RO water consumption. A chiller is the definitive solution but it costs money and consumes electricity.
In tropical freshwater aquariums the range depends on the species. Discus want 28-30 degrees. Neons live well at 22-25. Caridina cantonensis (crystal) prefers 20-24.
The ponds follow the seasons. In winter koi go into torpor under 10 degrees and stop eating. Feeding them in the cold is harmful because they don't digest. In spring the resumption of feeding must be gradual.
The brackish follows the rules of the marine with a little more tolerance: estuarine species are used to fluctuations.
Reference values by aquarium type
| Aquarium type | Recommended range |
|---|---|
| Marine (reef) | 24 - 27 °CReef: ideal 25-26°C. Never above 28 for SPS |
| Tropical freshwater | 22 - 28 °CDiscus: 28-30. Neon: 22-25. Crystal: 20-24 |
| Coldwater / pond | 4 - 22 °CKoi: under 10°C suspend feeding. Goldfish: 15-22°C |
| Brackish | 22 - 28 °C |
How it is measured
Digital thermometer with probe (the most precise). Suction cup thermometer (cheap but less reliable). Controller with probe (Neptune Apex, GHL) for continuous monitoring. For ponds, floating thermometer or wireless probe.
What happens when it is too low
Slowed metabolism. Tropical fish stop eating. Filter bacteria work to a minimum. The corals close. Plants slow down growth.
What happens when it is too high
Dissolved oxygen decreasing. Accelerated metabolism with more ammonia production. Bleaching in corals. In ponds, warm water encourages algae and reduces oxygen.
Coralia Lab monitors this parameter with AI diagnostics. Tank Score alerts you when a value moves outside the recommended range for your aquarium.
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