Wondering if I can get some opinions on some of the following.
Thought this was a sponge when I bought the piece of rock but it looks more like it has polyps. Sorry for the poor exposure, it is in a shaded part of the tank right now:
Looks a bit like an egg sack. I assume from some snails as there were several of these on the glass. I have cerith snails but these are not cerith eggs (I have seen those many times) as well as 3 kinds of nassarius snails, some trochus snails, astrea snails, a couple of margarita snails and 3 bumble bee snails. Any ideas what may have laid them?
Also these which are larger:
And finally this snail. it seems to graze on the glass and occasionally rocks. Haven't seen it bothering any corals.
Thanks in advance.