Symptoms of spawn fungus
external symptoms
- White or slightly brownish threads protrude from the fish eggs.
- Cotton-like formations on the fish eggs
photos
Photos: Andreas Werth
The pictures show fungal eggs of red witch catfish, from which young hatched despite the fungus. The first picture shows the eggs 5 days after spawning with fungal spores. The next two pictures show fungal eggs 6 days after spawning. The fourth picture shows a fish larva next to the fungal egg from which it hatched.
causes
Eggs react very differently to certain factors in the individual stages of development. It is often difficult to find the exact cause of spawn fungus. So mushrooms may develop better in acidic water. It is difficult to say whether a low pH value is really responsible for fungal growth or whether other factors are the cause.
Eggs that are either unfertilized or in which the embryo in the egg has died often fungus. However, the pictures show that larvae can also hatch from fungus-infested eggs.
If eggs become moldy within the first 24 hours of egg laying, they may not have been fertilized.
In any case, it is important that the eggs get enough oxygen. Therefore, an air vent near the scrim can be helpful. The eggs should be gently streamed. In the case of sensitive spawn, the spawn should be placed in its own aquarium, in which there should be no plants and no substrate.
The ion spectrum of the water, the osmotic conditions, i.e. essentially the water hardness, and the germ density in the water also play an important role.
If the water is too hard, the eggs z. B. deprived of water. The eggs dehydrate, meaning they dry out. The embryos in the egg die. Or the egg shell does not burst due to the osmotic pressure, although the larvae are fully developed.
Conversely, too much salt can flow into the eggs and thus into the cells of the embryos.
In some species of fish, the spawn is sensitive to light. In such cases, fungal growth can be prevented by darkening the aquarium. Photosensitivity disappears once the young have developed ocular points in the egg. The sensitivity to temperature and pressure fluctuations also decreases at this point.
treatment suggestions
In any case, possible causes for the fungal infection must be eliminated. The living conditions in the aquarium must correspond to the needs of the spawning fish species. Normally, no further funds are then even necessary.
There are always some fungal spores and bacteria in the water. With sufficient water changes, the germ density can be reduced to such an extent that no eggs become moldy.
With UV clarifiers or humic acids, e.g. B. from peat or alder cones, sea almond leaves, the germ density can be additionally reduced.
We have had good experiences with the following products:
Dosing experiences:
- Sea almond tree leaves approx. 1 leaf per 100 liters – the leaves should be changed after approx. 14 days
- Alder cones about 1 cone per 10 liters
Even under the best conditions, individual eggs can be unfertilized or die, causing them to fungus.
Further measures can only make sense if, despite the best conditions, whole clutches of eggs still grow fungus. First, unfertilized and fungal eggs are removed if they do not damage the clutch. Then, commercially available antifungal remedies can be used to prevent further fungal infections. Which means can be used in each case depends on the fish species. The eggs of some species do not tolerate certain agents.
For example, 3 per thousand sea salt helps with many killifish. For tetras, 3 milligrams of methylene blue per liter of water is recommended. Malachite green is also suitable. In the past, acriflavine was often used. It is currently used less frequently because it is suspected of being carcinogenic.