Cercariae, black spot disease, Black Ick (diplopstomiasis)


imageSymptoms: the fish, very irritated, scrapes itself against objects, has small black specks or smudges on the body and around the mouth, and if heavily infected may experience blood loss.

Cercariae refers to the larval stages of parasitic flukes (Trematoda). When the larvae encyst in the skin, the tissue reacts by depositing pigments on the parasitic cyst. This is perceived as black spots. Black Spot or Black Ick is rare in aquariums.

A worm species (Diplostomum) lives in the eye lens and eye fluid where it can cause cloudiness and blindness. 

Because the fish is only an intermediate host and fish-eating birds or mammals are the final hosts, these worms are usually unable to complete their life cycle, so that they cannot spread and are only found in fish living in the wild. Therefore, it can be introduced only when adding new fish into the aquarium. Fish that are most readily susceptible are the Silver Dollar, Piranha, or other fish of these types. In general it does relatively little damage to the fish, even if they are heavily infested.

Treatment (if necessary)

Black Spot is generally easy to cure. Either treat with salt baths or there are a number of commercially available treatments and preventatives.

Feed the fish sparingly during the treatment and remove any activated carbon from the filter. Switch off any UV-C appliances and CO₂ fertilizing appliances. Please also ensure that skimmers and ozonisers in saltwater are switched off. 50 % of the water should be changed prior to application of the treatment. Aerate the aquarium using a diaphragm pump with airstone during the treatment. 

After treatment

After the treatment, please filter the aquarium water for 24 hours using activated carbon to remove the residues of medication. Afterwards the activated carbon should be duly discarded. The addition of a bacterial starter to the aquarium water helps to replace any purifying bacteria which may have been affected.