Free Aquarium Stocking Calculator
Plan freshwater stocking in seconds - check bioload, fish compatibility, and pH & temperature fit. Free, no sign-up.
Not sure what to keep? Help me choose → · Got fish in mind? Tank size calculator →
Tank setup
Add fish
Tap a fish to drop it into your tank - set the number in your stock list below.
Filtration
Stronger filtration lets your tank safely hold more. Tell us your setup and we'll show the capacity boost.
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.
Tank visualization
Stocking summary
Select a tank and add fish.
Estimated care level
Add a tank and fish to estimate your maintenance load - water change frequency based on tank size, plants, bioload, filtration, cleanup crew, and high-waste species.
Compatibility matrix
Green ✓ compatible, Amber ! caution, Red ✕ avoid. Tap or hover a cell for the reason. Add 2+ species to see the matrix.
Compatibility is judged on temperament, predation, adult size, fin-nipping and overlapping water parameters - the same engine behind our species care guides. Individual fish vary; always monitor your tank and adjust.
Origin & biotope
Add fish to see origin match.
Recommended plants
Live plants soak up nitrate, oxygenate the water and give fish cover - a planted tank stays cleaner and supports a little more life. Here are plants suited to your tank, by lighting.
Low-light, no-CO₂ plants (shown by default) are the easiest start. Plant care guides · set your planting density in Tank setup to factor plants into the bioload.
Recommended setups
Not sure where to start? Tap a proven, compatible combination to load it instantly - then tweak to taste.
Like this Stocking Calculator?
Get the full version including a full suite of time saving AI tools. We keep things simple so you can spend more time focusing on enjoying your tanks.
About this stocking calculator
Use our online aquarium stocking calculator to plan freshwater tank stocking. It checks bioload, fish compatibility, and pH and temperature ranges. Explore freshwater species profiles for minimum tank sizes and temperament flags. It runs the same logic as leading fish tank apps like App-aquatic, with no sign-up required. New here? See how to use a stocking calculator, read about how stocking rules evolved from inch-per-gallon to bioload, or get the app to save tanks and track parameters.
Conservative by design. Our bioload calculation is deliberately cautious - based on years of fishkeeping experience and the science of bioload and tank capacity. Experienced keepers with strong filtration, plants and good maintenance can often exceed these limits; beginners may want to stock more lightly.
Related: Tank size calculator · How to use a stocking calculator · Free aquarium stocking calculator guide · How many fish per gallon · Overstocking · Data study: 71% of popular fish outgrow a 10-gallon tank · All guides
Stocking calculator FAQ
Is this aquarium stocking calculator free?
Yes - it's completely free with no sign-up or login required. Plan as many tanks as you like right here in the browser.
Is this a good alternative to AqAdvisor?
Yes. It uses the same bioload-and-compatibility idea but adds a fish compatibility matrix with plain-English reasons and a suggested fix for every clash, pH and temperature overlap, biotope matching and planted-tank adjustments - all on a modern, mobile-friendly interface. See the full AqAdvisor alternative comparison.
How many fish can I put in my tank?
Enter your tank size, filtration and planting and the calculator estimates a safe stocking level from litres, filtration turnover and plant uptake - using the same bioload engine as the App-aquatic app. See also how many fish per gallon.
Does it check fish compatibility?
Every pair of species is checked for temperament, predation, fin-nipping, adult size and overlapping pH and temperature. Conflicts show as caution or avoid with the reason and a suggested fix - the same engine behind our species care guides.
Is the stocking calculator accurate?
It mirrors the App-aquatic app's stocking and compatibility engine and errs toward safe, stable tanks. Treat it as a strong starting point and always monitor your own water parameters.