Most digestive disorders in fishes are caused by parasite infections. However, not all parasites cause problems for fishes -- some live in a symbiotic relationship with the fishes.
The symptoms can vary depending on the parasite causing the digestive disorders, but usually include weight loss, lethargy and loss of appetite. Young fishes are especially susceptible to digestive disorders and can die before any symptoms arise. Such parasites which cause these type digestive disorders include:
Protozoan parasites Spiionucleus and Hexamita infect the intestines of cichlids, bettas, gouramis, and other aquarium fishes. Apart from the symptoms listed above, fishes with these two parasites produce stool that is white and stringy. Cryptobia, another protozoan parasite, infects the stomach of African cichlids.
Various living conditions which can cause digestive disorders in fishes include:
A type of parasitic worm; it is flat and made up of segments
A type of relationship in which both parties are benefited
The condition of being drowsy, listless, or weak