Brought some clams and muscles home from beach and a crab or two?

I am a somewhat novice for saltwater setup. I have a 150G set up live rock and sand only with some mushrooms from another tank before(125g), a sea urchin and then have damsels, cardinal, a tang or two, a blow fish and a scooter bleeny, etc in my tank. I was at the beach and just for an idea grabbed a few crabs off the rocks, couple of muscles and some small dime size clams. The clams didn’t really make it after a day or two in the tank and finding shells opened and cleaned out by the hermit crabs. Possibly caused by a sand sifting starfish? Possibly because of having live sand instead of the finer beach sand they lived in? But they did bury themselves. Some muscles died and not sure if the others are alive or not at this point. Figured this would work because I bought a live rock with small muscles on them from a pet store and they are still alive. The crabs I see every so often eating some of the other dead muscles as they were dying one by one over the week. But not really recently. did not expect them to live since I believe they need to come out of the water for air possibly? Not sure if that is true since I did catch them on the rocks out of water. So what gives? What did I do wrong? Not that I was expecting them to survive but at least would like to know why they died. I even bought some Kent marine ZooPlex for the muscles. Maybe I need DT’s as well? My temp is good, PH and others testings are good, lighting is good, Just not sure what may have went wrong. Searching for advice if I ever was to do it again. Wanted to bring home a starfish but just wanted to start with a few more hardier specimens first to try out. Not looking for any insults or joking. Just looking for possible educated answers please.

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