About Fish Stocking Calculator
New aquarium owners often make the fatal mistake of "Overstocking"—adding too many fish to a tank. Fish produce waste (Ammonia), which is toxic. The filter bacteria convert this to Nitrate, but they have a limit.
The "Inch per Gallon" Rule
The classic rule of thumb is "One inch of fish per gallon of water".
Example: A 20-gallon tank can hold 20 inches of fish (e.g., ten 2-inch Tetras).
Limitations
This rule is flawed but useful as a rough guide for small, slender tropical fish (Tetras, Guppies, Danios).
It fails for:
- Bulky Fish: A 10-inch Oscar produces 50x the waste of ten 1-inch Neons.
- Goldfish: They are essentially "waste factories" and need double the volume.
- Territorial Fish: Some fish fight if they don't have personal space, regardless of water volume.
How to Use
Enter your Tank Size (Gallons) and the average size of fish you want. The tool gives a safe stocking number for community fish.