Aquarium substrate choice depends on tank type + livestock + plant goals. Inert sand (community FW): CaribSea Super Naturals, Black Diamond Blasting Sand, pool filter sand. Pros: cheap, never needs replacement, looks natural. Cons: doesn't feed plants. Use for tetras, livebearers, cichlids, corydoras. Aquasoil (planted tank): Fluval Stratum, ADA Amazonia, UNS Controsoil, Tropica Aquarium Soil. Pre-loaded with macro + micronutrients. Pros: explosive plant growth, lowers pH/KH (good for South American). Cons: leaches ammonia for first 2-3 weeks (cycle hard), depletes after 1-2 years. Aragonite reef sand: CaribSea Special Grade, Fiji Pink, Reef Saver Bahamas Oolite. Pros: buffers pH/alk, great for reef. Cons: cloudy when first added. Bare bottom: SPS reef tanks, breeder grow-outs, hospital tanks. Pros: easy waste removal, max flow. Cons: stark visual. What to avoid: colored gravel (toxic dye risk on cheap brands), crushed coral in freshwater (raises pH/hardness unintentionally), painted gravel in shrimp tanks.
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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