Free Aquarium Stocking Calculator — Online Tank Stocking Tool
Use our online aquarium stocking calculator to plan freshwater tank stocking. Check bioload, fish compatibility, pH and temperature ranges. Same logic as leading fish tank apps like App-aquatic. No sign-up required. How to use a stocking calculator — Get the app to save tanks and track parameters.
← Got fish in mind? Use our Tank size calculator instead — add species and we'll tell you the tank you need.
Our bioload calculation is conservative by design—based on years of fishkeeping experience and science around bioload and tank capacity. Experienced keepers with strong filtration, plants, and maintenance can often exceed these limits; beginners may want to stock more lightly.
Tank setup
Add fish
Filtration
Filter setup can increase bioload capacity. Capacity multiplier = how much extra bioload your tank can handle: 1.0× is baseline, 1.25× = 25% more capacity. Same logic as App-aquatic.
Override the calculated value. Enter 1.25 for 25% more capacity, 2.0 for double (max). Useful if you have heavy filtration, lots of plants, or experience with higher stocking.
Current stock
Tank visualization
Stocking summary
Select a tank and add fish.
Estimated care level
Coming soon: maintenance estimate based on messy fish, bioload coefficient, and stocking density. Will indicate how often you’ll need water changes, gravel vacs, and parameter checks.
Compatibility matrix
Green = compatible, Amber = caution, Red = avoid. Cells show compatibility %. Add 2+ species to see the matrix.
Compatibility scores are estimates; individual fish temperament varies. Always monitor water parameters and adjust stocking based on your tank's performance.
Origin & biotope
Add fish to see origin match.
Recommended setups
Curated tank + fish combinations coming soon. Select a tank size and we’ll suggest compatible species and quantities.
Like this Stocking Calculator?
Do far more in App-aquatic — save tanks, track parameters, build care schedules, and get reminders. Same stocking logic, full app experience.
Related: Tank size calculator · How to use a stocking calculator · Free aquarium stocking calculator guide · How many fish per gallon · Overstocking · All guides