I just purchased two snail from my LFS and I was told that they were olive snails. They told me they would be great to move around the sand for me but as I was waiting for them to acclimate in my tank I did some further research online about these critters. I got mixed statements that they might eat other snails in my tank. All i have as of now are astrea snails. Is this true? Are they more of a pest in the long run?