id please

okay everyone..... I tried to get a picture but it comes out blurry every time so I will try to explain best I can. In my refuguim I have this thing like a small snail with two tentacles on its head. It eats like a snail except it moves faster and it has a flat round shell that does not cover the whole body. It kinda looks like a spotted slug with a coorful red spotted flat shell on it. I thought I just had one but today I see 3, plus I can't find my urchin. Do I have something horrible?
 
I did more research and I think what I have is a stomatella???? does anyone know anything about these little guys?
 
that is exactly what they look like just not that color. Thanks so much. I always want to double check everything so I don't get in over my head. I guess I am a little paranoid!
 
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