Best way I have found for adding sand is to rinse it thoroughly and use a pvc
pipe and a funnel to get it to the bottom of the tank. Add maybe a couple cups at a time. Make sure you get dry sand and not live. The live stuff is usually not all that live and could cause a spike in the tank. Try adding a few nassarius snails to help with the sand bed.
If the skimmer is running properly it will be bubbling into the collection cup and will need to be emptied usually weekly.
where is the clown swimming? Some gobies tend to do that.
Post some pictures and we can help with the coral IDs