Temperature requirements vary by species' native habitat. Tropical community (tetras, rasboras, gouramis, platys, corydoras): 76-78°F (24-26°C). Stable temp matters more than exact number. Bettas (Betta splendens): 78-82°F (25.5-28°C). Lower temps suppress metabolism + immune system. Discus: 82-86°F (28-30°C). High temp accelerates metabolism + reduces parasites. Plan tankmates carefully - few species tolerate this range long-term. African cichlids (Lake Malawi, Tanganyika): 76-82°F (24-28°C) depending on lake. Mbuna run cooler than Tanganyikan species. Goldfish (common, comet, fancy): 65-72°F (18-22°C) for fancy. Common + comet tolerate 50-78°F. Cold-water (white clouds, dojo loach, hillstream loach): 65-74°F. Reef tank: 76-80°F (24-27°C). Stable to within 2°F. Above 82°F = oxygen depletion + coral stress. FOWLR: 78-82°F. Slightly higher tolerable than reef. Saltwater fish-only: 76-82°F. Temperature stability: use 2 thermometers (digital + glass) - they cross-validate. Replace heater every 2 years. Use Inkbird controller for redundant safety. Heat waves: in summer, drop tank lid for evaporative cooling, run a fan over surface, freeze water bottles + float (matched temp). Cool back gradually - rapid drop is also stressful.
The full Q&A library answers the most-searched aquarium questions. Browse calculators, glossary, and disease database for related help.