Where Did My Fish, Crayfish, Frog or Shrimp Go When They Perform the Vanishing Act?
Fish, frogs and crayfish may disappear from your tank with no sign of them anywhere. Where did they go? There are a number of options!
Some species of fish are likely to have jumped, crawled or flipped themselves out if you don't have a enclosed top. Among these are swordtails, rainbowfish, frogs, salamanders and crayfish. They may also climb up air tubing and filter tubes to get out. Look in dark corners, under furniture and in dust bunnies for these escapees. If they are still alive, put them back in the tank. They just might survive! Others you may not find until months later, dried up. Unless the critters are large, you are not likely to notice a smell. If you have other pets, they may find a (not -so-tasty) treat on the floor.
Some amphibians and invertebrates (crayfish) will try to escape during rainy periods as that is when they typically migrate to other locations. My newt would only try to escape when we took him to our cottage when the water body was nearby. At home in the city, he never attempted to escape.
Eaten by Larger Fish
If you have fish of different sizes in one tank, even if they have lived harmoniously until today, the bigger ones may have eaten the smaller ones. Maturity, hunger and stress are the key reasons that fish who ignored each other suddenly
eat a tank mate. A small fish grows up and gets to a size big enough to consume small fish or shrimp. Smaller fish swimming around in a frenzy or is injured can trigger a predatory response in a formerly peaceful fish. Bettas and dwarf aquatic frogs may eventually eat smaller fish and baby shrimp.
Trapped in Decorations
Fish can get trapped in decorations designed for shrimp. These decorations have lips and ledges that prevent fish from getting out the bottom or small windows in enclosed areas with ledges at the top that confuse fish and trap them inside. If there are snails or shrimp in the tank, they can clean up the trapped bodies before you find them.
Make sure to take the decoration all the way out of the tank. We only discovered a missing guppy and Corydoras (who liked to hang out together) after my husband took the decoration all the way out to drill larger door and window holes and remove the edges from one house decoration. Their bodies were found inside the upper section. He also drilled out the floor of the upper level so the fish could sink down and get out the bottom opening that did not have a lip.
Corydoras catfish have a natural tendency to go down under things, not up over ledges so we don't have any decorations that have lower ledges anymore. A guppy's tendency is to swim upwards so we also can't have any lips on the top side of the closed areas. (see photo at the top of the page) We have seen that many, many people have lost fish in decorations and also had fish injured scraping themselves against them. Be careful in your choice!
Sucked up Into Strong Filters or Water Pumps
If you have small fish and strong filters, they may get sucked up the intake. Placing a small sponge filter on the intake and turning down the flow can prevent this.
Swim Up Into Hang on Back Filters and Sponge Filter Tubes
Fish that enjoy fast water flow may swim up the outflow of hang on back filters and into the filter itself and get trapped there. Guppies, loaches and other fish love to play in the current. They may also swim down into sponge filters against the current as well. You can place some filter floss in the top of sponge filter tube to prevent them from getting inside the tube.
Some fish are burrowers and will dig into sand, gravel and under rocks. This may be a natural behavior for them even though it's new to you. Do some research and find out what their typical behavior is.
Other species are nocturnal and may be shy. Malaysian trumpet snails are like this. They burrow in the gravel to feed during the day and come out at night. Many catfish are nocturnal or prefer the twilight hours. If you are not watching at those times, you may not see the fish. A simple fix for these is to use a red light. LED and CFB come in red. The red appears as low light level to them and so they get active.
Cave breeders may disappear for weeks on end during the day to protect and clean their eggs and fry. If you have deep caves or well-planted tanks, they may be tending to their young. I place the openings facing forward so we can see inside.
So, you see, there are many reasons why a fish might disappear from your aquarium. You might have to do some sleuthing to find out that they are still there or where they might have gone!