Fungus – the ever present danger – to fish and eggs
There are many species of aquatic fungus but by far the most common two are saprolegnia and achlya.
Symptoms of fungal attack
Fungus occurs as white, grey and sometimes brown fluffy growths on the skin or fins of fish or on developing eggs from a spawning.
Saltwater fish actually suffer less, than freshwater fish, from fungus because of the salt in a marine environment. However, brackish water fish, even mollies, when kept in insufficiently salty water are the most prone to fungal attacks.
Fungus often starts as a small tuft, and usually spreads when not treated and can kill a fish if the fungus penetrates the internals of the fish. Fish eggs if not treated or infected eggs are not removed can cause all nearby eggs to be infected and killed.
What causes fungus to develop
Fungus and fungal spores thrive in damp environments with decaying organic matter and an aquarium is full of water so is ripe for fungal outbreaks. Fungus sprouts where there is decaying organic matter, dead fish, or unfertilised or dead fish eggs. When fungus grows it releases millions of spores into the water which will quickly infect any fish that has a break in its protective mucous which may occur after rough handling or an attack from another fish or bumping into aquarium rocks.
Parasitic diseases such as ich, body ulcers and infections will damage the protective mucous and allow entry of fungal spores, compounding the fish’s problems.
When fish are kept in poor quality water conditions with water that is full of bacteria, nitrites, ammonia and excessive fish waste then they are much more likely to get infected by fungus.
Fungus treatment for fish eggs
With fish eggs any unfertilised eggs or dead eggs will quickly get infected with fungus. If that egg is not quickly removed then the fungus will spread and infect otherwise healthy eggs. All adjacent eggs may be killed.
Prevention of egg infection by fungus is achieved by adding methylene blue to the water immediately after the eggs have been spawned. Be careful not to overdose because eggs may suffer developmental problems. Also remove any off-white eggs with a pipette before they become heavily infected.
Cichlids actually do a good job in removing dead and unfertilised eggs and keeping the eggs free from dirt as part of their parental care.
Fungus treatment for fish
Treat as soon as possible. use an aquatic antifungal remedy from your local aquarium shop. Place any heavily infected fish in a quarantine tank and treat the fish there. In the main aquarium a dose of salt added to the water should heal slightly infected fish and help to kill of most spores present.
Prevention is better than cure and this is a mostly preventable illness. Remedy the environment of the aquarium that led to the original outbreak. If it was an accident such as a dead fish then a salt dose to the aquarium should be sufficient.
However, if the cause was rotten food then you must keep up good feeding practices of not feeding more than the fish will eat. Observe all the food you place into the aquarium and remove any uneaten food with a siphon. When your aquarium has a nitrite or an ammonia spike then fish will go off their food. If you feed at this time then you will surely cause a disaster.
Make sure your filter is fully cycled. Make sure that the water you add to the aquarium has the chlorine removed before adding. Also, siphon through and disturb the gravel to remove any build up of fish waste. And make sure your filter has not become clogged. If the filter is clogged then squeeze out the excess dirt from the sponge into a bucket of aquarium water.
And finally, keep up good maintenance practices. Then you should never have a problem with fungus again.