What is this?

[SoggyBoi]

It's growing on my rock and glass

it looks almost like tiny cauliflower.

 

[grumpy-crab]

I'm almost positive that's snail eggs... its a good thing. ;-)

 

[NanaReefer]

Looks like Sponge :)

 

[Squishie89]

I can't tell in the first picture, but probably sponge. Second picture is snail eggs.