How Fungus Attacks Eggs
Saprolegnia spores float in every tank. They colonize unfertilized or weak eggs first, then spread to healthy eggs nearby if water flow is low.
White cottony growth on the egg surface is the visible sign. Affected eggs die within 12 to 24 hours.
Methylene Blue Protocol
Dose 2 drops per gallon of pharmaceutical-grade methylene blue into the spawning tank the moment eggs are confirmed.
The blue tint prevents fungal spore growth without harming developing embryos. Water becomes transparent again after 24 to 36 hours.
Never use methylene blue with biological filtration — it kills nitrifying bacteria.
Acriflavine Alternative
Acriflavine at 3 to 5mg per liter works similarly and is less staining.
Prefer this in tanks with live plants.
Water Flow Tactics
Gentle airstone placed 5cm from egg cluster prevents spore settling.
Some breeders use pH 6.5 soft water specifically because fungal spores reproduce slower below pH 7.
Manual Removal
If a fungused egg appears, remove with a pipette immediately. Every removed egg is ten healthy eggs protected.