JBL's research team has been sent rare pictures and a few questions which are of interest to all aquarium keepers: Fungi or moulds as the cause of diseases are not exactly popular among aquarium keepers. However, there are also rare species of "fungi" or "moulds" that are harmless and have a very unique way of life: The slime moulds or slime fungi (Eumycetozoa).
Slime moulds possess features of both fungi and animals. Despite their name, they do not belong to the fungi or moulds, and instead, represent a separate line of development in evolution. The common features of the slime moulds comprise amoeboid locomotion (plasmodium), which can sometimes be rather fast, and transformation of the plasmodium into spore-bearing fruiting bodies. They feed on litter (detritus) in the aquarium by engulfing the food particles and then ingesting them (phagocytosis).
Of approx. 1200 recognised species, only a very few can live aquatically i.e. underwater on a permanent basis. The genus, didymium, which may be rare in aquariums with different species, is one of these groups. Species of didymium live outdoors on hydrangeas among other places, so that they are not found exclusively underwater.
In an aquarium, they tend to live on the bottom where the aquarium keeper doesn't notice them. They do occasionally come out of the underground, though, spreading over rocks, roots and aquatic plants in the form of white mesh networks. In this phase, they can reach speeds of up to several centimetres per hour, so that they can appear in different places and then disappear again quickly. Combating them with remedies like e.g. JBL Fungol Plus 250 or other remedies against fungal diseases has no effect.
They are harmless to plants and fish, so that they do not pose any threat. If you wish to remove them from your tank anyways, the only option is to disinfect the tank completely with JBL Desinfekt and replace or disinfect all of the furnishings, since they exhibit enormously high growth rates and can regenerate from the tiniest of fragments.