Methodology
Every result on Aquarium Forge is reproducible. This page documents the formulas, assumptions, and rule versions behind our tools, so you can always trace a number back to its source.
Volume & Water Change
Rectangular volume = L × W × H, converted at 231 in³ per US gallon. Actual water volume applies your fill percentage. Glass displacement is not subtracted.
Substrate & Gravel
Volume = footprint × depth. Weight uses typical bulk densities: gravel 1.68 kg/L, sand 1.6 kg/L, aquasoil 0.75 kg/L; gravel types range 1.5–1.6 kg/L. Weights are estimates — real density varies by brand and moisture.
Weight
Water ≈ 1 kg/L, reduced by substrate displacement. Glass = panel area × thickness × 2.5 g/cm³ (soda-lime), open-top assumption. Freshwater basis; saltwater ~2–3% heavier.
Heater
Linear model: watts/gallon ≈ 1.5 + 0.175 × ΔT(°F), rounded to standard wattages and shown as a range. Large tanks or large rises trigger a two-heater recommendation.
Filter
Recommended flow = volume × turnover (freshwater 4×, planted 3×, heavy stocking 5×, reef 8×). Minimum shown is 3×. Manufacturer rated flow differs from operating flow — always noted.
Stocking Algorithm v1
Bioload = Σ(adult size × activity factor [0.8/1.0/1.3]) per fish, compared against gallons × filtration factor [0.8/1.0/1.15]. Independent rule checks: species minimum tank, schooling group size, temperament conflicts. Output is a Planning Status (Understocked → Overstocked) with issues — never an absolute verdict. Algorithm version: v1 (2026-09).
Compatibility Engine v1
Five checks in order: temperature overlap, pH overlap, temperament, adult size/predation ratio, minimum tank for the pair. Well-known combinations carry editorial verdicts with exceptions. Output levels: Compatible / Conditional / Not Recommended. Engine version: v1 (2026-09).
Editorial review
Species data carries a source name and a review date on every page. Guidelines follow widely accepted hobby standards (community stocking practice, manufacturer sizing conventions, and NIST conversion factors). When guidance is genuinely contested — as with stocking density — we say so and explain both sides instead of picking a number quietly.