FastAquatics

Fish tankmate compatibility guides

10 compatibility guides for popular aquarium species. Each guide lists compatible tankmates + species to avoid + the WHY behind each recommendation.

What fish go with Betta?8 compatible · 5 to avoidWhat fish go with Goldfish?5 compatible · 5 to avoidWhat fish go with Freshwater Angelfish?6 compatible · 5 to avoidWhat fish go with Discus?5 compatible · 5 to avoidWhat fish go with Oscar Cichlid?6 compatible · 5 to avoidWhat fish go with Cherry Shrimp?6 compatible · 5 to avoidWhat fish go with Ocellaris Clownfish?7 compatible · 5 to avoidWhat fish go with Guppies?7 compatible · 5 to avoidWhat fish go with Mollies?6 compatible · 3 to avoidWhat fish go with Platies?7 compatible · 3 to avoid

Aquarium-keeping fundamentals

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.

Frequently asked questions

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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Saltwater livestock · Freshwater livestock · Coral catalog · Care library · Q&A library (222) · Glossary (127) · Disease database (50) · Calculators (29) · Interactive tools (7) · Husbandry deep-dives · DIY projects · State legality directory