Filter choice depends on tank size + bioload + livestock type. Hang-on-back (HOB): AquaClear, Seachem Tidal, Marineland Penguin. Best for 10-40 gallon tanks. Pros: cheap ($25-80), easy maintenance, customizable media. Cons: visible from outside, water-evaporation noise, limited capacity. Canister: Fluval 07 series, Eheim Classic + Pro4, Oase BioMaster. Best for 40-150 gallon tanks. Pros: 4-stage media customization, silent, hidden, large capacity. Cons: $130-400, complex maintenance, can leak if seals fail. Sponge filter: Hikari Bacto-Surge, Hydro Sponge. Best for shrimp tanks, fry tanks, hospital tanks. Pros: $5-20, gentle flow won't suck up shrimp/fry, biological powerhouse, near-zero maintenance. Cons: ugly, no mechanical filtration. Internal: Tetra Whisper, Fluval U-series. Best for budget setups + breeder tanks. Pros: cheap, all-in-one. Cons: takes up tank space, low capacity. Reef sump: Trigger Systems, EShopps. Best for reef tanks 75g+. Pros: hide skimmer + heater + ATO, dramatically increased water volume, refugium space. Cons: $200-1,000, requires drilled tank or overflow box, plumbing complexity. Capacity rule: filter rated GPH should be 4-6x tank volume for FW, 8-15x for SW.
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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