Keep fish for long enough and you are bound to come across an internal parasite infection in one of your aquariums. Internal parasites infect almost all fish species and are often continually present in natural aquatic environments. Symptoms of internal parasite infections often include; fish developing swollen abdomens, fish becoming gaunt/skinny, loss of colour etc. These symptoms are less obvious than those of external parasites, which are clearly visible to the naked eye. While there are medications on the market to treat internal parasites, these medications often target a limited number of parasite species and with no easy way to identify the species of parasite infecting your fish, this may present an issue.
However, there is an easier, medication free, way to treat internal parasites. Internal parasites feed off the food that the fish ingest, this deprives the fish of much needed nutrients, eventually resulting in the death of the infected fish. However, if you are able to deprive the internal parasites of their food source it is possible to kill them. The easiest way to do this is to starve the fish. While this may shock of few people and sound counter-intuitive, fish are able to go substantial lengths of time without eating, with few-to-no side-effects.
If you choose to utilise this method of treatment, I would suggest starving smaller fish, such as tetra’s, for a period of seven days and larger fish, such as cichlids, for a period of 14 days. If treated early on, almost all of the fish should recover, however, if left too late, the most affected individuals may succumb to starvation. Under normal circumstances, healthy fish would be able to endure this starvation period with zero losses. This method can also be combined with medication for an increased chance of successful treatment.