20 Gallon Aquarium Stocking Calculator
The 20 gallon is the sweet spot for planted community tanks — enough volume for a diverse ecosystem without being overwhelming to maintain. This calculator accounts for your filtration, plant density, and species waste output to give you an accurate stocking score.
Aquarium Stocking Calculator
Calculate bioload, check compatibility, and plan the perfect stocking for your tank.
Add your tank & fish
Your stocking score will appear here once you enter tank details and add some stock.
Your stocking score says how full the tank is. This says how well it would do — Finn scores stocking, water, maturity, equipment and compatibility, and tells you what to watch.
It's a simulation of a tank on paper, so treat it as a planning estimate. A tank you actually track scores far more accurately.
Add your tank size and at least one species first.
Aquarium Type
Tank Dimensions & Volume
Calculated: 19.9 gal (75.3 L)
Filtration & Setup
Oversized filtration adds bonus capacity.
Tank Age
Older tanks tolerate higher bioloads.
Stocking
Stock List
Popular species:
Search for fish, shrimp, corals and more to build your stocking list.
Save your stocking plans
Create a free account to track your tanks, log water parameters, and build your dream stocking list.
Hey! I'm Finn 🐟 Tell me what you're going for — like "a peaceful 20 gallon community" or "betta paradise tank" — and I'll set everything up for you. You can also ask me to analyze your plan once you've filled it in.
Popular stocking ideas for your 20 Gallon tank
🌱 20 Gallon Planted Community
A classic planted community with neon tetras, pygmy cories, and a cleanup crew.
🦐 20 Gallon Shrimp Tank
A dedicated shrimp breeding setup with dense planting and gentle sponge filtration.