CUC

[minkin]

Currently in my 30g tank I have 2 clowns and 2 chromis.

My CUC is 1 cleaner shrimp, 1 peppermint shrimp, 5 hermit crabs and 5 snails.

Is this CUC enough or do I need more?

 

[mr_X]

It's enough.

 

[minkin]

Thanks.

Also one more question, do my invertebrates need any supplements like iodine etc?

 

[mr_X]

Nothing more than what's in your salt mix. A water change replaces any lost elements. I've been doing things that way for quite a few years now and have had good results.
Don't add anything to the tank without being sure you need it.