Do they contribute to the bioload? Yes, everything does. Does it mean you can't have more fish because of the snail? That depends entirely on the circumstances. It would really only be a concern in small tanks. In a larger tank, like a 29, adding a nerite or two would not impact the number of fish you could keep. In a small tank like a 5 or 10, it may. But then again, such small tanks should not be housing that many fish to begin with, so in my opinion the snail will not impact the number of fish a small tank can house because the tank size is the limiting factor for your fish stock.
Bioload is only a problem if you do not have enough surface area to sustain a colony large enough to handle it, or you are unable to keep nitrates in check performing water changes. As long as you are getting 0 ammonia, 0 nitrites and your nitrates are not escalating out of control, your bioload is fine.
forum community dedicated to tropical fish owners and enthusiasts. Come join the discussion about species,breeding, health, behavior, aquariums, adopting, care, classifieds, and more! Open to fish, plants and reptiles living in freshwater or saltwater environments.