How the Stocking Calculator Works
This calculator analyzes your fish selection against your tank size using several factors: bioload capacity (how much waste each species produces relative to tank volume), temperature and pH compatibility between all selected species, inter-species compatibility (temperament conflicts), and schooling requirements for shoaling fish.
The bioload gauge shows how full your tank's biological capacity is. Planted tanks get a 25% bonus because live plants absorb ammonia and nitrate, effectively increasing your filtration capacity. For optimal fish health, aim to stay below 75% — this leaves room for growth and provides a buffer against water quality issues.
General Stocking Guidelines
The old "one inch per gallon" rule is outdated and unreliable — a 10-inch oscar produces far more waste than ten 1-inch neon tetras. This calculator uses bioload factors that account for each species' actual waste production, body mass, and metabolic rate. Always pair adequate filtration with your stocking level, and perform regular water changes using test kit readings as your guide.
Need Help Choosing Fish?
Browse our complete fish species guide (53 species) for care requirements, or check our compatibility checker for detailed pairing analysis. For your first tank, our beginner guide walks you through everything step by step.