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The old “one shrimp per gallon” rule is far too conservative for dwarf shrimp and far too generous for big filter-feeders. This calculator uses species-specific ranges that experienced keepers work with, adjusted for plants, tank maturity and tank mates, to tell you how many shrimp to start with and roughly how many the tank can carry long-term.
How it works
Dwarf shrimp have a very small bioload, so the real limit is food (biofilm and algae) and water stability rather than filtration. We start from a per-gallon figure for each species, then:
- reduce it by 30% if the tank is lightly planted (less grazing surface and cover),
- reduce it by 40% if fish share the tank (competition, predation, extra waste),
- and warn you if the tank is too new or smaller than keepers generally recommend.
Stocking guide by species
| Species | Minimum tank | Start with | Long-term density | Breeds in freshwater? |
|---|---|---|---|---|
| Neocaridina (cherry, blue dream…) | 5 gal / 19 L | 10 | up to ~10 per gal | Yes |
| Crystal / Taiwan bee (Caridina) | 10 gal / 38 L | 10 | up to ~8 per gal | Yes |
| Tiger shrimp (Caridina) | 10 gal / 38 L | 10 | up to ~8 per gal | Yes |
| Amano | 10 gal / 38 L | 3–5 | ~1 per 2 gal | No (larvae need brackish water) |
| Ghost shrimp | 5 gal / 19 L | 4 | ~3 per gal | Rarely in home tanks |
| Bamboo / wood shrimp | 20 gal / 76 L | 1–3 | ~1 per 5 gal | No |
Why start with 10 or more?
A group of ten gives you a good chance of both sexes and enough genetic variety to avoid a colony that stalls. Breeding shrimp self-regulate: when food runs short, fewer females carry eggs. Adding more shrimp than the tank can feed usually shows up as a slow die-off weeks later, not immediately.
FAQ
Can I keep shrimp in a 2.5-gallon tank?
Neocaridina can live in small tanks, but temperature and parameters swing fast at that volume. If you do, keep numbers low, top off daily with remineralized water and avoid heaters without a thermostat.
Can I mix Neocaridina colors?
You can, but different Neocaridina color lines interbreed and within a few generations most offspring revert to brown or clear. Keep one color per tank if you want to keep the color.
How many shrimp for algae control?
Amano shrimp are the best algae eaters: about one per 2 gallons in a planted tank handles most soft algae. Cherry shrimp help too, but mostly graze biofilm.
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