For beginner like you.
Is better to start-up with common clownfish (scientific name Amphiprion ocellaris)
This fish are hardy and easy to keep compared to other marine fish.
And it is also among the easiest marine fish to maintain,feed, and breed.
The common clownfish is ideal for keeping with invertebrates such as shrimp.
Their diet are omnivorous and like most meaty foods such as shrimp,mussel and also take flakes food.
And require water condition :
Temperature 24-26 C (75-79 F); pH 8.3-8.4; SG 1.023-1.027.
After you mastered the technique you can keep Domino (scientific name Dasyyllus trimaculatus) and Blue devil (scientific name Pomacentrus coeruleus)
Hope you like my advise and opinion given.
Good luck with your new fish and fishkeeping hobby
