What to look for in a new fish
by Dan

There are certain things that are important to look for when selecting a healthy specimen to bring home. Some fish can appear healthy in the LFS and soon become unwell once brought home. So, you need to know what to look for in a fish…

Selecting a healthy fish is not a hard thing to do but it does require patience and restraint. If your not 100% sure that a fish is healthy I would recommend you don't buy it.


Firstly, you need to make sure the specimen is swimming with vigour and strength. A healthy fish will be alert and looking for food most of the time. It should not appear lethargic or resting on the base of the tank (apart from species that do this naturally, e.g. Hawkfish or Gobies).

Disease or Injury

They should not be damaged or have any visible injury such as lesions or cuts.

Whitespot is a major risk when introducing a new fish (which is why it is wise to quarantine). This infection can wipe out entire tank populations of fish which has led many to leave the hobby. If a fish is infected with whitespot it will appear to be covered in tiny pinhead sized dots, and they quickly lose weight.
Velvet can also be introduced through new fish. Its name is basically as it appears – like a velvet coating over the infected addition. Quarantine can again be very useful in clearing up this infection.

It would not be recommended to purchase a new introduction in this state.

Picture by James141

Doing a search on UR can bring up many ways to deal with these problem infections, and show just what the costs can be if new introductions are not quarantined.


It sounds obvious but the amount of people who have not seen a fish actually feeding in the LFS that bring it home to watch it slowly starve is astounding. I cannot stress this enough, you need to make sure a fish is feeding before making the purchase. If a fish has a disease it can at least be treated, however, if a fish is not eating, it is rare for them to start feeding again.

An example of an underweight Zebrosoma flavescens (Yellow tang).

Picture by eskimoigloo

Some species do not feed well or gather enough nutrition in our tanks, such fish as polyp eating butterfly fish, some sand sifting gobies and Mandarins are also poor survivors where not enough food is available. These species will be covered in another article.


It is necessary to know whether a new introduction will be harassed by former tank occupants before buying. Most species will not take kindly to a new introduction of the same genus being introduced to their territory. In most cases they will fight, sometimes to the death. Even if the level of aggression to a new tank member is low it can cause them to retract into the rockwork of the tank and not venture out for food, this is more of a secondary way of death through incompatibility.
Some fish are just naturally more aggressive towards any other later introductions than themselves; these species should be added last if at all.
Ask about compatibility with your tank, with your corals, and with your other fish.

So, now you know what to look for in a fish, so no excuses! If you are not sure about a fish do not impulse buy. Go home and research it. If you have any questions at all please ask on the site, we are happy to help


-A good book I have found priceless when looking for a new specimen is ‘A PocketExpert Guide to Marine Fishes' by Scott W Michael.

-Ask at the shop how long the fish has been there. If they have quarantine facilities in place, what temperature and SG they have been kept at, all this information will help with acclimitasation.

-If its possible put a deposit down on the fish and return to collect it at a later date. Also, you could visit the fish on different days to view its health over the course of a week or two.

-Find a shop that you trust, and where you believe disease is at a minimum, and buy from there.

-Tank bred fish are known to be hardier and will most likely settle down faster than wild caught specimens.