Snails up the whazoo

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I don't understand why snails can't propagate and multiply in an aquarium.

In freshwater aquaria there are several different species of snail and all of them multiply rapidly, in fact a common FW problem is snails multiplying out of control.

If SW snails won't maintain self-sustaining populations in an aquarium you would have to ask why. Could the problem be not enough nutrients, lack of an essential element, a toxic water contaminant, or predation? And do people with refugia have snails propagating in them?