Fish often rub against solid objects and leap out of the water. It is possible that they do this to catch flies or get food or they may be playing. However, in the majority of cases, it is because something is irritating them. This may be a minor irritation, similar to an itch in humans, perhaps but it could be more serious. Whether you should act or not, depends on the numbers affected, the frequency of rubbing and leaping and the vigor involved. If one or two are having a lazy rub on the bottom drain, there is no cause for concern this is fairly normal. But if they are continually tearing about, rubbing vigorously against the sides or bottom or leaping out of the water, then further investigation must be carried out.

Unfortunately, one of the most common responses to this type of behavior is to suspect a parasite problem and an anti-parasite treatment is administered, without further thought. But this cursory diagnosis or guess, overlooks the fact that any irritant can cause this response, including poor water quality. A high nitrite level for instance. Where upon using an anti-parasite treatment can only make matters worse.