Easily 75-100 RCS (mix of adults & juvies), assuming the tank is well aged.
If you are really looking to breed RCS, a few things to keep in mind:
- they will breed better (faster, larger broods) if your water is on the alkaline side and has some decent hardness to it.
- having a substantial amount of moss (java moss or something similar) helps provide food for the shrimplets and is the best/most important plant to have in a shrimp breeding tank.
- sponge filter is far superior to any other option for a filter. Not only will it provide food (grazing) for shrimplets, it is the only filter kind that doesn't pose a danger to shrimplets. HoB or canister filters with uncovered intakes (i.e. no sponge covering) will be the death of tiny shrimp.
- while planted tanks generally thrive at higher nitrate levels, dwarf shrimp breeding does better at low nitrate levels (less than 10 ppm). Thus there is often a trade-off between water parameters for your plants to thrive and water parameters for your shrimp to thrive. You need to make a choice about which you want to favor.
- be sure to avoid fertilizers with copper, and be cautious about dosing iron, as both are toxic to shrimp at levels way lower than they are to fish. It's also best to check the ingredients on any food you plan on putting in the tank and, if anything containing copper is listed (e.g. copper sulfate as a preservative), at least consider moving to a different brand of food. (Note opinion is split among shrimpkeepers about whether the low levels of copper introduced by food have any negative effect. YMMV.)
RCS are the "rabbits" of the dwarf shrimp world, they really do breed like crazy when given the right conditions.
