You have purchased a new fish, placed the bag in the aquarium for twenty minutes, and then released the fish into their new home. Everything seems fine, as your new acquisition is getting along swimmingly with the other aquarium residents. Then one day, the fish is gone, without a trace. Its not floating at the top of the tank, nor is it stuck to the intake tube of the filter. The fish simply disappeared. Has this happened to you? Are you wondering where the fish went? Let's explore the possibilities.
Fish Often Jump
This seems like the obvious answer, but jumping fish can end up in surprising places. The fish often don't stop moving once they hit the floor. They may wiggle and flip themselves under a piece of furniture, sometimes very far from the aquarium. This is especially true of fishes from the labyrinth family (bettas, gouramis) and other fish that are used to shallow, oxygen-starved bodies of water. The author once found a swamp dragon under a piece of furniture 20 feet away from the aquarium it jumped out of 6 months earlier.
Something Could Have Eaten the Fish
Once again, this seems obvious, yet the culprit who is eating the fish may not be as obvious. The general rule of thumb is that if one fish can get another in its mouth, it will. Even if one fish could barely fit the other fish into its mouth, it may still try. This is especially true if the fish was sick, or if the fish was new and didn't quite know its environment.
Fish that would not normally go after other fish may eat a dying or decomposing body of a former tank mate. Even plecos, which are primarily vegetarians, are known to munch on a dead fish in the aquarium.
Check the Filter
It may seem impossible for a fish to get sucked up the intake tube of a filter, but it happens. When fish are sick and on their way out, they often have trouble swimming away from the current created by the intake pipe of the filter. The fish ends up stuck to the tube, and as it dies and decomposes, gets sucked right into the filter.
Though it may be too late you save the fish, you should still check the filter, as the dead fish may impede the filter from working properly, or negatively effect the water quality of the aquarium.
Check the Aquarium Decorations
When fish become ill, they often seek a place to hide. The fish who has disappeared from your tank may be hiding in an ornament or the crevice of a rock. If the fish dies while hidden, it could decompose and be eaten by other aquarium residents without you even noticing. Once again, it is wise to check these places for any remains, as the fish who has passed on could effect the water quality of the tank.
If you've looked everywhere and can't find the fish, decomposition may have gotten to it before you. What actually happened will forever remain a mystery. You will probably want to buy a new fish to replace the one that mysteriously disappeared.
Before replacing the fish though, do some research to make sure it was right for your aquarium in the first place - maybe the pH was too high or too low for that fish, or maybe you added some salt to the aquarium, and that specific type of fish has a low tolerance for salt. Perhaps the temperature was too low, or too high.
Test the water in the aquarium. If the water quality has degraded over time, the older fish in the tank may have built up a tolerance to the water conditions, while the new fish may not have been able to handle them, and died soon after.
If there is anything positive about having a fish disappear from a tank, it is that it gives the aquarist an opportunity to check the water parameters, and make sure that everything in the aquarium is in working order. If something has gone awry with the water chemistry of the tank, the mystery of the disappearing fish may not be such a mystery after all.
References
www.aquariumadvice.com/forums/f17/the-case-of-the-dissappearing-cardinal-and-neon-tetras-h-49115.html
Ian Shoust - With a degree in Communications and a certificate in Digital Video Editing, Ian Shoust has worked as a freelance videographer, editor, and ...
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