The 8 reef-tank mistakes that kill coral. Stable parameters, light, flow, and sourcing.
Daily alk swing >1 dKH/24h triggers RTN in SPS. Test 2x weekly during dosing dial-in; once/week thereafter. Never make corrections of more than 0.5 dKH per day.
SPS demands stable parameters + clean water + high flow. Master soft + LPS for 6-12 months first; build the discipline of weekly testing + dosing before adding SPS.
Every coral piece carries hitchhikers (AEFW, red bugs, nudibranchs, flatworms, vermetids). Dip in CoralRx/Bayer for 5+ minutes. Quarantine for 30 days. Costs $0.50; saves $500+ in coral collection wipeouts.
A reef tank under SPS lighting (250+ PAR) with budget LEDs = bleached + STN coral. Either match lighting to livestock requirements or stick to LPS/soft coral.
Tanks without an Apex/Hydros controller fail silently when heaters stick on or ATOs malfunction. Controllers + alerts pay back the first incident.
Hydrometers drift 1-3% within a year. Use a refractometer (calibrated monthly with 35 ppt solution). Salinity-shock from a drifted hydrometer kills corals + fish.
A new reef tank cannot support its full bio-load. Add fish + coral over 6-12 months, not 6 weeks. Watch parameters after each addition; let them stabilize before the next.
Tap water carries phosphate, copper, nitrate, and chloramines that fuel algae and kill coral. RODI is mandatory for any reef tank, period.
Browse the full common mistakes library.
Whatever specific topic brought you here, four fundamentals govern long-term aquarium success: water quality, parameter stability, biological filtration, and species-appropriate husbandry. Skip any one and the others struggle to compensate.
Water quality: ammonia + nitrite at zero, nitrate under 30 ppm freshwater + 10 ppm reef. Test weekly with API or Salifert kits. Use our water parameter checker to score your readings against your tank type.
Parameter stability: stable wrong parameters beat fluctuating ideal parameters. Most fish tolerate a wide pH range if it's stable. Sudden swings of 0.4+ pH or 5+°F kill fish faster than chronic suboptimal values. Use temperature controllers (Inkbird) + automated dosing for consistency.
Biological filtration: the bacterial colony on your filter media + rock + substrate is the engine. Never replace all media at once. Use our filter turnover calculator to size correctly.
Species-appropriate husbandry: research adult size, territoriality, diet, and tankmate compatibility before purchase. Use our tank stocking calculator + compatibility guides.
How long does an aquarium take to set up? 4-6 weeks for full cycling + first stocking. Use our cycle ETA calculator + how long does cycling take.
What's the best aquarium for beginners? 20-gallon long. Big enough for parameter stability, small enough for budget + space. See beginner picks.
How often should I do water changes? 25-30% weekly. See water change frequency Q&A + water change calculator.
Why does my fish keep dying? 5 leading causes: uncycled tank, wrong species pairings, no quarantine, undersized tank, neglected water-change schedule. See full diagnosis.
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