When the aquarist obtained the desired fish for the display aquarium hopefully time was spent observing them. Just because fish are ‘new’ and in a dealer’s sale tanks does not mean they are problem free. This isn’t having a go at dealers at all; fish can have problems that don’t become apparent sometimes for weeks. The point of purchase is the initial line of defence.
The aquarist should look for fish that have bright eyes, unblemished skin, clear fins and a rounded body. Any fish with blemishes or spots on the skin or fins is suspect, as are cloudy eyes. Most marine fish are active and visit all parts of the aquarium, so a fish that is skulking in a corner is also suspect. The breathing rate (watch the gill beat) should be normal, though this can be a little difficult as different fish have different rates. However, it is often fairly obvious if a fish has an elevated breathing rate. There could be a good reason for this, such as bullying and harassment with nothing actually wrong with the fish. Caution though is the order of the day. There isn’t anything wrong in asking to see fish feed, particularly if the fish is a known or possible problem feeder. If feeding is a known potential problem this fish is not for the beginner.
Fish chosen should be compatible with each other and any that are already owned. Failure to choose such fish can lead to harassment causing stress. Obtaining fish unsuitable to the tank environment also causes stress, for example surgeon fish need plenty of swimming space. Stress could lead to disease.
It is assumed that the fish are properly and successfully introduced to the display aquarium and all is well. They all feed properly and get on with each other. Everything from this point on should be fine. Nowadays it is easy (compared to much earlier years) to maintain high quality seawater. A large number of aquarium fish do not encounter disease, probably the majority.
Besides maintaining the aquarium to the highest standards, it is the responsibility of the aquarist to keep a watch on the fish. This is easy as one of the greatest pleasures is simply observing beautiful fish and also perhaps a thriving coral reef. Seeing the fish isn’t a chore. They need to be examined though, not just looked at, for a little while. Are they all present? If not, which is missing and how long before it re-appears? If it does, is it acting normally? If it doesn’t, maybe it has died. Is there any ammonia present (mostly unlikely with modern bio filtration)?
Are the other fish acting normally? Do they have any marks or spots on the body or fins? Any cloudy eyes? Any increased breathing rates? Are they all feeding as usual? Is the swimming style of each fish normal or are any displaying unusual motion?
Taking the time to spot anything unusual, even though it may seem not much, is good husbandry. Treating some ailments, particularly in a reef aquarium, isn’t easy. The earlier a potential problem is spotted the earlier a diagnosis can be attempted. Some problems are easy to diagnose, others not so.
A simple check as described when observing the aquarium is worthwhile and could under certain circumstances prevent a population of fish being wiped out. Not a pleasant thought!
It must be mentioned that sometimes a fish will scratch on a rock and the aquarist, particularly a beginner, may twitch with apprehension. Most fish occasionally rub a rock probably for the same reason humans scratch an itch sometimes. It doesn’t necessarily indicate a health problem. Similarly, a mark may be seen on a fish’s skin – this could be where the fish has caught a rock. A watch on that particular fish will often indicate that there isn’t a problem.
Fish in our aquariums live in a tiny world compared to their wild home. For ongoing wellbeing they rely entirely on the aquarist. Maintenance and observation is a very small price for a living display of such beauty.