So, do you like hermit crabs? How about snails? Or shrimp? I happen to love inverts so i always have a good amount, usually anyways. lol
I would add maybe 5-10 hermits (make sure you get extra shells, they kill each other for the shells)
and maybe 5 snails. I like the nassarius snails, they dont eat algae but they live under the sand. When you feed the tank they pop up like magic and look for the food. I love those guys.
And shrimp, just depends on your budget. Fire shrimp are bright red but about $30 each. Cleaners are nice too, maybe $20-$25 each. And peppermints are only a few bucks and active peppy little guys.
I would stay away from turbo snails, they are too big for that tank. Is there any other inverts you liked or saw that you had questions on?