Added some extra things from the beach this weekend. Just a few small clumps of calcified stuff (largest was a little bigger than my hand), which had tubes of what looked like fan worms/mussels or something. It was night so I didn't see exactly what loose stuff i was picking up.
When I got home and checked in the light I had a bunch of various types and sizes of crabs too. They all went in. maybe 10 - 12 in total. Smallest was about 1cm (majority were about 3cm. One big boy was 8cm.
I noticed snails yesterdays, and this morning I saw three small sea slugs. (two the same species, the other looked very different).
On the few pieces of stuff I took there was also quite a few different types of algae, a few different types of green, and then some grass like red algae which covered most things.
These last few days the tank has exploded with life and stuff I didn't see initially. The Mollies are loving it too haha.