How can I be so sure? Well, fish are living organisms and therefore have a timed lifespan. On the wild reef this could be cut short by a predator. In the [tag-tec]home aquarium[/tag-tec] there aren’t any predators capable of taking other livestock, or there shouldn’t be. So how does the fish disappear?
The aquarist quite rightly checks the fish when doing routine maintenance or feeding. It is at this time that the absence is noted. Has the missing fish previously not been quite right – swimming strangely, breathing badly or similar? Are the other fish up for their food as usual, and swimming around as usual at other times with good colours? Are the water parameters normal and up to spec? Definitely no sign of ammonia or nitrite?
If there’s nothing wrong as in the previous paragraph then the fish has either been suffering from some malady that does not affect the others or, simply, its time has arrived. Apart from size, it is difficult to know the age of a wild caught fish. It may be months old, or years. Also, I am not aware of the expected lifespan of fish. It seems reasonable to assume that they might live longer in a well managed aquarium, with the lack of predators, but the potential lifespan, how long is it?[tag-ice]Reef fish[/tag-ice], when faced with a reduction in health, often swim into the rockwork to find safety. This is their natural response. Of course, it may well be that the fish never comes out again. The aquarist has to assume after a few days that the fish is lost. Is there anything to be done?
There is no need to dismantle the reef in an attempt to locate the fish, and I doubt many aquarists would be tempted to do this. Leave the reef as it is. However, do not go out and purchase a replacement, at least not yet. In a mature reef aquarium the tiny life forms present can dispose of a dead fish very quickly. In a less mature system these life forms may not be present in number so disposal will take longer. The aquarist should not alter the routine [tag-self]aquarium maintenance[/tag-self] schedule, but ensure that water changes continue and the schedule includes regular ammonia/nitrite checks. These checks should be done daily once the fish is known to be lost. After four or five days reduce to every two days. After around a week and a half all should be well. This period is there to allow any consequence of the sudden appearance of a dead fish to appear. If it does not, all is well. If ammonia or nitrite is detected, observe the fish and ensure they are comfortable and not displaying signs of stress. Be prepared to do additional water changes. The bio-filtration is tuned to the normal load, and the additional load may not be successfully fully dealt with.
Once the period of water quality stability testing has passed, then a further fish can be considered and purchased.
The loss of a fish is a sad occasion for the aquarist. Even with excellent water quality and excellent nutrition, and the aquarist carrying out maintenance diligently and correctly, these losses occur. The fish however may have lived longer than it would have done on the wild reef.