Aquarium lighting serves three roles: visibility, photoperiod (day/night cycle for fish health), and photosynthesis (plants + corals). Fish-only freshwater: any 5-15W LED gives the fish a normal day/night cycle. 6-8 hour photoperiod. Avoid leaving lights on 24/7 - it stresses fish + grows algae. Low-light planted: 20-40 PAR at substrate. Anubias, java fern, crypts, vallisneria thrive. ~25W LED on a 20-gallon long. 7-9 hour photoperiod. High-light planted: 60-120 PAR at substrate. Carpets, reds, demanding stems. Twinstar, Chihiros WRGB II, Aquasky 2.0 G7, ONF Flat One+. CO2 mandatory at this level. 8-10 hour photoperiod. Reef tank: 200-450 PAR depending on coral type. Softies need 50-150 PAR, LPS 150-250, SPS 250-450. AI Hydra, EcoTech Radion, Reefi Uno, Kessil A360. 8-10 hour photoperiod with sunrise/sunset ramp. Photoperiod consistency: use a programmable timer or smart plug. Inconsistent lighting causes algae blooms and stresses fish. Sunrise + sunset ramps reduce stress and look natural.
The full Q&A library answers the most-searched aquarium questions. Browse calculators, glossary, and disease database for related help.
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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