If this is going to be the first marine fish in your new marine setup then there’s one of 2 roads to go down.
1. Get a damsel these are the cheapest fish you an get which are pretty hardy and easy to look after. Unfortunately this makes them a testing fish, in the means of if theres an issue they will float and die.
I’d recommend taking your water to a local Marine shop and get them to do a full water test on your water. first before you put any fish in.
The thing is with damsels is they look pretty but are little cunts they’ll fight between them selves and with other fish. So if 1 year down the line you are find these blighters hard to catch your likely to have a tank full of fish. so for this reason i’d steer clear of damsels as tester fish or even all together.
2. I got a pair of Tank bred common Clown fish, costing around £25 for a pair. I had my water fully tested my my local supplier and everything was fine and i wait around 3 weeks after setup before adding these fish.
When ever your choose a new fish there’s a few things you need to take into consideration.
1. Tank Size
If you’ve got a 90 litre nano aquarium then don’t be expecting to get a lovely Regel Tang as they need alot of room in terms of litreage easily 240 litres as a minium as they grow large a Red Sea Max 250 would be ideal.
Is ny new fish foing to be aggresive towards my current fish. Picasso Trigger fish can be picked up for around £20, but they can be an agressive fish and will eat smaller smaller fish.
Some fish such as Tangs tend to nip at soft corals so if your really worried then coral nipping fish are best avoided.
Foxfaces are a lovely looking fish but they have a toxin in the spin on there fin so this cud end up in a trip to Hospital if your stung. Also Boxfish look cool due to there shape but when they feel threatened they will release a posin that in the sea quickly dissapates but in your tank will stay around and could result in a complete wipeout.