I’ve Lost A Fish!

The fish only aquarium or reef aquarium has been stocked. The aquarium may be fairly newly set up, or may have been running for months or years. Sooner or later, a fish is going to disappear.

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.


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7 Comments
  1. I recently gave up on my 180 gal. saltwater tank.
    I jsut got sick of losing all those very expensive fihs that I had
    I always bought the very best and exotic fish.
    I was a collector for most of my life.

  2. Really happy I came across this blog!

  3. Hi Chris, really happy your pleased. 🙂

    Hi DD2. So sorry that you have given up the marine hobby. 🙁 It must have been heartbreaking to finish. If being a ‘collector most of your life’ means that is the period you have run a marine aquarium then I am puzzled as to your losses taking into account this experience. Such losses suggest problems beyond natural lifespans.

  4. This reminds me of the latest fish we lost. My dad bought a goldfish for our tank (which was filled with tropical fishes like tiger barbs, janitor fishes, and this thing you call paciato) 3 days ago, and it only lasted 20 minutes. The tiger barbs must’ve thought his tail was a fish flake, so without further comments, you can now imagine how we lost it 😥 . Sad, those were supposed to last for years, and it didn’t even make it on the first day in our tank.

    anyway, asside from the lost of pet, I do wish you a great weekend.

    cheers always,
    ~m

  5. From my own tropical freshwater days (a long time ago) I remember Tiger Barbs as they were attractive, and also problematic if they were with any fish with flowing fins, such as many guppies. I was also advised to keep the barbs in odd numbers to reduce in-fighting. Until then I hadn’t realised that fish could count 🙄 !!! I have always believed goldfish to be cold water fish??? Could this have contributed to the loss?

  6. I’ve been advised that goldfish, though coldwater, can tolerate some elevation in temperature provided oxygen availability is watched. It was suggested that I think of a goldfish in “cold” water in a warm room – what temperature is the water?
    Yes, ok, I get it!

  7. I have a 55 gal reef tank for about 2 months now. I do regular water changes. I regularly check salinity, temp and nitrites/ates ammonia and PH. The soft corals I have placed in the tank are all flourishing and growing. I did stock my tank with a number of fish and as of this week I have lost 2. A royal gramma and a blue-yellow damsel. Both had been in my tank for over a month and I thought well acclimated. It does break my heart that they just disappear… I appreciate your article and I was mildly tempted to break the reef down a bit to see if I can find them or mebbe if I have an unwanted predator.

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