4 themed stocking plans with exact species + counts + notes. Pick the theme that fits your goals, then verify with the stocking calculator.
Notes: The 36"x18" footprint allows real aquascape with multiple coral zones. Best entry-level reef size.
Notes: Discus-only setup with tetra dither fish. RODI + soft acidic water. Daily feeding = active growth.
Notes: High-tech planted with CO2 + EI fertilization. Carpet plants + stems + epiphytes.
Notes: Multiple territories form. Breeding triggered by water changes + temperature drop.
Use the stocking calculator to verify the exact species + counts work in your 40-gallon. Also check the water change calculator for ongoing maintenance, and the setup guide library for the full build playbook.
Browse all stocking idea pages from 5g nano to 180g show-tier. Or jump to the stocking blueprints for build-along plans with timelines.
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.
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