concern about fish

[Ricky1066]

I am beginig to worry about my clown fish I have had him over a week all me readings have been 0 except nitrates which were 20 now down to 10 .
The fish comes out to eat swims around about 5 minutes then goes back under rock he seems to just sit therelittle wiggle here little wiggle there.
Is there something to wrry about.
I have the clown fish and yesterday I bought 5 turbo snails

[Avi]

Fish that are alone in a fishtank may perceive the absence of any other fish as an instinctive sign that danger is near. Consequently, they tend to remain in whatever shelter is afforded them. So, long as the fish is eating when you put food in, it is probably just fine and when you start adding other fish into the tank, it will come out more and more.