Tide Pools and Mussle ID?

[fretfreak13]

I went to St. Petersburg FL a few years ago, long before I got into saltwater tanks. While my brother and I were trying to build a sandcastle, we went down to the waterline where the water recedes and leaves the sand wet, and dug some up for castle report. What we found were really cool! Amazingly colored mussles that, once you put them back on the wet sand, they wiggle and burrow until they're covred again. We alsofound a few "bugs" which scared the hell out of me, but now I know what they are. SWF sells them as sandsifting crabs.
My questions are would both these little crabs and mussles be good sand sifters for an aquarium? Also, is it leagal to take them from the beach? There are millions of them. In every handful of sand we turned over, there was at least twenty mussles, and in every five handfuls there was at least one crab.
Also, does anyone know where it's legal to collect from tidepools? I'd like to maybe bug my family to go somewhere like that on vacation this summer. Posted below is a picture of the mussles, and something else we found swimming in the water. We picked it up and it felt like a slug. it was about as big of the palm of my hand, and when it was placed back in the water it used its flaps of skin, I guess, to swim. Looked like it was flying. I don't want it in a tank, just to know what it was. We named him Slugbob Mushpants. =P

 

[kingtriton]

those mussels are coquinas, they don't do well in the aquarium...I had brought a handful home after snorkeling one day and put them in the tank, the died pretty quick...they have a really specialized diet and need to be in the surf to filter feed. They do make good food for your fish though

...my hermits opened them up and then it was a big coquina party in my tank lol...oh and they make for excellent soup!!

that slug creature looks like some sort of sea hare, not sure though...but that's what it looks like. Ive seen many of them swimming along the shore, but not sure how they would do in the tank.