Large zebrafish are infected with female anchorhead worms, and the adult bugs can be plucked off one by one, but this is a long process and potentially harmful to the fish. A short soak in a 3% salt solution can also remove the worms from individual fish. There are now aquarium treatments that kill the adults. Also in ponds, repeated use of the antiprotozoal treatment can kill the larvae. Adult worms can also be killed with trichlorfon.

Large zebrafish are infected with black spot disease, and new anti-parasitic treatments kill the parasites, but once black spots form, they leave traces. The most effective preventive measure is to break the parasite's growth cycle, by ensuring that water birds are not near the pond or aquarium, and that no parasite-infested snails appear.

The big zebrafish was infected with fungal disease, in the aquarium, passed the test Whether the water is in good condition, at the right temperature, and not too alkaline (a pH 7.2 is best for freshwater aquariums) can prevent possible infection. Many treatments are recommended, but some of them have serious disadvantages. Saltwater bathing is a traditional treatment for freshwater fish diseases, but can cause undue irritation, require frequent changes, and is not particularly effective alone. Methylene blue is effective in mild cases, but the prescribed amount can stain the water, making it difficult to keep checking the progression of the disease. Malachite green can also be applied to the infected area. There are several new specialized treatments that are generally effective against fungi.