As far as your stocking list goes, the clowns can go in no problem. A hippo is completely out of the question without a 6ft long tank that's at least 2ft wide and tall. A yellow tang is also not a great idea but can sometimes work in that size (they will only survive 5-10 years vs 20 in a larger tank). The mandarin is only doable if you have a large refugium in your sump and don't add any other POD scavenging fish (like wrasses excluding fairy) and don't even think about adding a mandarin until the tank is 1.5 to 2 years old. You can add a nem, but need to wait until you have had sucess with lps coral (1-2 years tank maturity) Any of the below fish would work well if you want the focus of the tank to be the clowns and mandarin.
- fairy wrasses
- dartfish
- anthias
- basslets
- cardinalfish
- chromis
- algae blennies
- gobies
- with caution dwarf angels or squirrelfish varieties
- reef safe wrasses (if you don't get a mandarin only)
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