for the week of 10/20/99

Why do fish jump out? Without delving too far into fish psychology, it’s safe to say that some fish have learned to take to the air to avoid predators, and others have learned to slither across land to other bodies of water. They may simply resort to these behaviors whenever they are stressed, or in unfamilair territory.

When do fish jump out? Sometimes, they are frightened when first added or when the aquarist is cleaning or otherwise messing around in the tank, and fly out right in front of him. But more often, they slip out overnight, or more specifically at dawn. When the tank is dark and the room is light, any openings in the cover must be like beacons. Fish are also most likely to escape during their first night or two in a new tank.

Which fish jump out? Almost all fish can, but some of the most likely are swordtails, elephant nose, koi, hatchet fish, spiny eels, rope eels and most gouramis. A few other creatures, like fiddler crabs, newts and mystery snails don’t exactly “jump,” but climb, crawl or slither their way out, instead. Placed into a poorly covered aquarium, most of these will certainly be gone the next morning.

How do you keep fish from jumping out? The obvious answer is to make sure the aquarium cover is adequate and remains closed – especially for the first few days. Openings for airlines, filters and heaters should be cut as precisely as possible, and any remaining gaps covered. Even a dime-sized opening makes an inviting target.

What do you do when fish jump out? If they haven’t been out too long, many fish recover nicely when they are put back in water. Carefully pick up the fish (preferably in a wet net) and place it back in the tank. If it shows signs of weak movement, gently pull the fish back and forth through the water, forcing fresh water through its gills. If it begins recovery, keep an eye out for other fish picking at it and for signs of infection.

“Tip of the week” appeared regularly in 1999 and 2000.