Does anyone know what this thing is?

[Loganberry98]

I'm very new to reef keeping. This is a 7 gallon tank with live rock. This thing started growing around a month ago and grew pretty quickly but hasn't grown much past this size. It's around the size of a quarter right now. Is it a sponge?

 

[Baldyreef]

definitely seems to be a sponge, although I must say I don't know what type ( I suck at sponge Id lol)