It depends on the species, and conditions of the aquarium or pond

In a marine REEF aquarium nitrates should be kept as close to 0 ppm as possible. In a fish only marine aquarium you should strive to keep your nitrates below 20 ppm.

There are many saltwater aquarium fish species available. Some of the more popular fish species include: Angelfish, Batfish, Butterflyfish, Clownfish, Dartfish, Frogfish, and Lionfish.

It is a marine species of fish.

According to the The Definitive list of the Marine Fauna and Flora of the British Isles and Surrounding Seas. Edited by Christine Howson and Bernard Picton there are 325 marine fish in UK & Irish waters