Remember this is only 5 gallons. Your list was rather long LOL
I would not do a clownfish, as they do get approx 3 inches minimum. You might get away with a single, or pair of dwarf seahorses or something. I would not do anemones - they are too sensitive and demanding - with such a small tank, slight changes can kill everything in it within minutes or hours.
Forget the anemones and clowns. Try live rock (with standard flourescent lighting), caulerpa, and a few catalina gobies. They'll accept frozen BS, graze on LR small inverts, and may even spawn in that small unheated tank.
uhmm
you can have LOTS of dwarf seahorses in a 5 gallon
not just a pair
or you could do an anemone depending on your light, i would just go with a conylactin
and a junk of liverock
and a clown should be fine
just one tho
but it wont go in the condylactin
If you get a 25w pc u can have zooanthids , mushrooms , pep shrimp, neon and or catalina gobys, green star polyp, candy cane , bubble, small hammer or torch, small frogspawn, a lot can be done but u will def need to be on your toes with w/c and contsantly checking your params.