Why do fish always die in the most awkward places?

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Ever wondered why fish seem to die in the most inaccessible spots of your aquarium – like under that large piece of bogwood, which then means removing half the décor? Neale Monks explains...

There are several reasons that can explain why this seems to happen. The first is that most fish float, so after death their corpses are carried by water currents into places where that current is weakest. This location will usually be in the corners of the tank, behind rocks and wood, or behind the filter.

A second reason is that other fish will push them into odd corners. Scavenging catfish and loaches will nibble on corpses, and, as they do so, they’ll end up pushing them about. Eventually that corpse will get wedged somewhere that the scavengers at least can’t dislodge.

A final reason is the behaviour of the sick fish prior to its demise. One common symptom of disease is shyness and, in the case of schooling fish, a tendency to break away from the group. Why they do this isn’t clear—perhaps they’re driven away by the healthy fish, or maybe they can’t participate in behaviours that maintain status and territories.

However, it’s common enough that sickly fish are most likely to be found hiding away in caves, under plants, or at the top of the tank behind filters and pipes. Should the fish die, its corpse may well end up in precisely these parts of the tank.

So while this question might seem a bit academic at first sight, it’s actually something worth thinking about.

Counting fish first thing in the morning and making sure they’re all exhibiting natural behaviours is a commendable habit of the good and caring fishkeeper.

A fish you can’t find might be dead, sick or stressed, and a missing fish is therefore a warning something’s up with your aquarium. It’s a signal that you need to check social behaviour, water chemistry and quality, and that all your equipment is in working order.

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