bivalve

I have lots of unknown items that keep popping up in my tanks, and I am just curious what some of them are specifically. I am going to upload all the photos. The top and bottom left are the same coral. It is all alone and appears to be some sort of monti cap or a mushroom maybe? The middle and...

I found this (large) bivalve in an amazing zoa colony. Is it reef safe? Should it be removed? The colony is currently being dipped in coralrx- will that kill the bivalve and require it's removal? (So it doesn't rot)

Just setting up a 90 gallon and bought Live Rock. The LR is covered with huge bivalves. There must be at least 10 of these in my tank from 2 to 5 inches - see pic. Are these hard to keep and/or will they just die and contaminate my tank?

This just appeared. Lol! Can anybody identify it? It's about an inch long and is attached to that white rock. Here's a little closer shot:

I have a few bivalve hitchhikers on my live rock, right now its all i have in my tank so i want to let them thrive for a few months. Does anyone know what they eat or how to feed them. I have heard they like dirty water, since i dont have anything else would letting my water getting a little...