If you can, please get a better color picture. I want to say vermetid snails too but it's kinda hard to tell. If they are vermetid snails then you could potentially run into some problems down the road...but you could also be fine. They are filter feeders and depending on who you ask they are fine. BUT some people believe they are the plague and regret ever letting any survive because they can completely take over. If you maintain your tank well and keep nutrients down they probably won't overrun it. They are also a problem because they can irritate corals in a number of ways one of the worst is because they will settle in on the corals themselves.
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