What are the tank dimensions (length x width x height)?
Don't waste your time with a UV steriliser.
Protein skimmers help remove protein from the water and keep it cleaner for longer. Protein creates ammonia, so the less protein, the cleaner the water. Protein skimmers are good to have but not essential. If you plan on having filter feeders and live corals with only a few small fish, then you don't need one.
Marine tanks have a pH of 8.4-8.5.
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Don't keep crabs in tanks unless it is specifically for crabs and nothing else. Crabs cause problems in marine tanks. Small hermit crabs are the only exception to this. They are ok but don't have normal crabs in tanks.
Only keep 1pr (1 male & 1 female) anemone fish/ clown fish in each tank. They are territorial and fight.
No wrasses in coral tanks unless they are fairy wrasse or small species of wrasse.
Keep Bangaii cardinals in groups of at least 6 (preferably 10 or more). In the wild they occur in family groups that live among the spines of black sea urchins. You don't need a sea urchin for them though. They are easy to breed and you can sell any you produce.
All Anthias can be a pain in the butt to get feeding. Most species fail in aquariums unless you get juvenile fish and feed them lots of different live foods. They also need to be in groups of 10 or more. However, if you get them feeding and they do well, they are stunning looking fish.
Start culturing rotifers and other small things to feed them.
Bicolor dottybacks are similar to Royal grammas but usually cheaper. Most dottybacks are quite happy to breed in aquariums and they usually do well in pairs. Some species can change sex so if you get 2 small fish, they normally become a pr.
Most pygmy angelfish pr up too, or a male might have a harem of 3 or 4 females.
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Corals need lots of bright light. What sort of light unit do you have on the tank?
Soft corals like leather corals are usually better for the beginner compared to hard corals like Acroporas.
Coral morphs (Corallimorpharia sp) are pretty easy to keep and there are some quite colourful varieties now.