fish egg fungus treatment

How To Treat Fungus on Angelfish Eggs

If you notice your angelfish eggs have turned white, this is bad news. It’s not a natural stage in the growth process, nor is it a minor issue. It means that fungus has overtaken the egg and killed it. The fungus will now spread to your other angelfish eggs and destroy the entire clutch, if allowed. The good news is, there are ways to stop this.

To treat fungus on angelfish eggs, you should clean the tank. This involves replacing 10% of the water every 2-3 days while scrubbing down the aquarium. Change your filters and remove any dead eggs, using a pipette, tweezers, or a needle. Chemical treatments should be applied to eliminate the fungus itself, so that it doesn’t begin infecting the other eggs. Options include methylene blue, acriflavine, hydrogen peroxide, potassium permanganate, iodine, or rosemary extract.

To prevent it from coming back, you need to maintain a clean, healthy, well-balanced tank, since fungus thrives on dead cells and waste. You should keep the temperatures under 84 F, maintain the pH balance, and clean the tank regularly. Placing the eggs in a safe location without fast-moving water can also help safeguard them against fungus. If you trust the parents, it’s best to keep them in the tank so they can clean fungus off the eggs.

Why Do Angelfish Eggs Turn White?

Angelfish eggs begin as small and round with a soft amber color. If they suddenly turn white in your tank, you may wonder if this is a natural part of the growth process. In fact, it means fungus has overtaken the egg and it is now dead. There is no way to recover the egg or reverse the process.

Angelfish eggs can fall victim to fungus for multiple reasons, the most common being:

  • The eggs were never fertilized and have now rotted, attracting fungus
  • There are fungal spores in your tank that have latched onto an egg that was weak from genetic issues or a thin shell
  • There is an overabundance of fungus in your tank and your angelfish eggs don’t stand a chance

According to the International Journal of Veterinary Science and Medicine, the fungus Saprolegnia parasitica is one of the most common to attack angelfish eggs. It comes from the genus typically known as cotton mold, which gives it a fluffy white appearance. Like most water mold, it thrives in fish tanks because of ready access to dead cells and fish waste. Eggs are vulnerable, making them another easy target.

When fungal spores come into contact with the egg, they will penetrate the shell. They will burrow deep into the inner yolk and destroy it, spreading further to encompass the egg. Soon, the entire egg will white or fluffy. Fungus can spread rapidly; the first egg will be used as a basecamp to infect surrounding, healthy eggs.

Within a short amount of time, it’s easy for all your angelfish eggs to be dead and white. That makes it important to keep a close eye on them. If you spot the first trace of whiteness in your eggs, take action.

How To Stop Fungus Growing On Fish Eggs

Cloudy water is a sure sign that there is fungus present in the breeding tank. It won’t take long before it becomes thicker around the clutch of eggs themselves. On the other hand, if the spores are not yet out of control, there may be very few signs that your angelfish eggs are now in danger.

The good news is, your solution is the same no matter what. You can stop the fungus from taking hold by:

how to stop fungus growing on fish eggs

Cleaning The Tank

The direct approach will involve changing the water in your fish tank so that you can remove a portion of the spores. Keep in mind that you should change no more than 30% at one time. You might shock the fish or eggs otherwise.

You should also thoroughly clean the tank. Be sure to scrub down the walls, clean the sediment or rocks at the bottom, and tidy up decorations. Fungus will try to grow anywhere it can find food. This will mainly include the bottom of the tank, on decorations, and around the filter.

On that note, be sure to change the filters, scrub down the unit, and thoroughly remove any spores you find. Your filter may have already been trying to remove the fungus. However, if it was overwhelmed, it may be cycling the leftover spores back into your water.

Changing Tank Water Regularly

Since you can’t change more than 30% of the water at once (without endangering your fish), keep up the cleaning routine.

  • Once a week, change the water again at 25-30%.
  • You can also try to swap out 10% every 2-3 days.
  • If the situation is dire, carefully change 5% every day.

Keep in mind that cleaning the tank every day might stress out the adult angelfish, causing them to eat the eggs. Likewise, if the changes are not made carefully, and the water’s chemical balance isn’t maintained, the eggs may die on their own.

Making drastic changes could remove the fungus before it’s too late, but it may also cause damage. You’ll need to decide how drastic you’re willing to be about this. For a safe bet, go with 10% every 3 days, which keeps the changes small, not too frequent, but still effective.

Removing Diseased Eggs

Dead eggs cannot be saved, so you must remove them before they infect the others. Since angelfish eggs are laid in clutches, you will need to pick out white ones carefully. Others may be damaged if you try to do this with your hands, a pen, or other objects. Recommended tools include:

A Fish Egg Pipette

A fish egg pipette is the smaller version of a turkey baster. These can be found in pet stores, but you can also use actual turkey basters to suck up the fungus-coated fish eggs. Just be sure the nozzle isn’t too wide, or else you risk damaging the other eggs. Here’s how:

  1. Carefully dip the pipette into the tank
  2. Place its nozzle in line with the white egg
  3. Apply pressure to the bulb of the pipette
  4. Wiggle the pipette to loosen the egg
  5. Continue until the egg is sucked up
  6. Lift it out of the tank, release the bulb, and deposit the egg onto a bowl.


This has more room for error, but will also be a more easily accessible tool. Using a pair of tweezers, dip your hand into the tank and gently squeeze the diseased egg.

Keep in mind that angelfish eggs are fragile. Too much pressure may crush it, spreading the fungal spores into the water or damaging other eggs.

Wiggle the egg back and forth until it loosens. Once it has, gently lift it from the tank at a slow pace and then dispose of it as you please.

A Needle

You can also carefully loosen the white eggs with a needle. Gently prod the edges and underside of the dead egg with the fine point. If it doesn’t appear to move, then poke at it from multiple angles, so that it lifts cleanly. Once it’s free, you can remove it by hand or with tweezers.

Fish Egg Fungus Treatment

Fungus can only be completely eradicated with chemical treatment. This can be through professional medication or home remedies.

Once you’ve cleaned the tank and removed the diseased eggs, consider these treatments. They will kill off any remaining spores and keep your angelfish eggs safe.

Methylene Blue

Methylene blue is used for the treatment and prevention of fungus on eggs and fry. Also referred to as methylthioninium chloride, it destroys parasitic and fungal infections without damaging the fish themselves. It’s also safe to use for other aquatic animals.

Many fish keepers use it in their tank as part of the cycling stage. This prevents fungi from ever taking root. So long as you follow the instructions, it will not upset the chemical balance of your tank. Just handle it carefully, since it can stain anything it touches.

  • The average dose is 1 teaspoon of methylene blue per 10 gallons of water.
  • For higher concentrations, add an extra 1/3 teaspoon per 10 gallons.
  • Just one application is enough.


Acriflavine is the second leading antifungal chemical that helps remove growths. It was originally used as an antiseptic, and can still be used as a topical treatment. However, its main use is as a fungicide, safe for aquariums and angelfish eggs alike.

You do not need to remove the parents from the tank during treatment, and it can be applied directly, following the instructions.

Hydrogen Peroxide

Hydrogen peroxide is a colorless liquid that breaks down the molecules found in the spores and kills them. Aquarium owners claim that it disinfects the eggs and may even save newly infected (but not yet dead) eggs from getting overtaken.

According to The Progressive Fish-Culturist, hydrogen peroxide can be a safe fungicide for aquariums, so long as you proceed with caution. The effects do vary depending on the species of fish and the tank conditions.

Larger fish tend to be more sensitive. The peroxide may also become slightly toxic if the temperatures in the aquarium are particularly high. Angelfish do like slightly balmy water, so if you have a species that prefers a higher range, consider other options.

Potassium Permanganate

Potassium permanganate can be used for destroying built-up bacteria, fungi, and parasites in the aquarium. It is recommended that you use this very carefully, however. It can be lethal to all your fish in high doses, the eggs included. Follow the instructions closely.


Povidone iodine is effective in treating a fungal infection on angelfish eggs. It has antibacterial and antifungal properties. You can apply it to the eggs, or spread it around them, without harm several times. This is helpful when you’re treating a newly infected tank and need to safeguard your clutch.

However, you should dose this carefully. Iodine is a toxic substance when applied in high dosages. Only 0.006ppm levels are safe for a fish tank. Always use a test kit to check the iodine levels in your aquarium as you treat it.

Rosemary Extract

According to The Journal of Natural and Engineering Sciences, rosemary extract can improve the lifespan of fish eggs. Not only does it work to boost their development, but it mainly keeps fungal infections at bay and fortifies the eggs against future spores.

In the study, rosemary was tested alongside methylene blue, iodine, potassium permanganate, and other medicinal herbs. It was the most effective in decreasing bacteria and increasing the chances of eggs hatching quickly.

Fish Egg Fungus Prevention

Once you’ve dealt with the fungus in your angelfish tank, it’s normal to worry that it’ll come back. Luckily, there are ways you can fortify your tank (and your eggs) against another outbreak of fungus.

Keep The Parents Present

New angelfish parents are notorious for eating their eggs, so many owners choose to separate eggs from the clutch. However, the parents can also play an important role in cleaning the eggs of fungus.

The mother and father alike will pick away at spores and eat any growths before they take hold. An experienced breeding pair is less likely to eat the eggs. If you can trust them, let them take over the job.

why do angelfish eggs turn white?

Good Egg Location

The placement of the eggs in your aquarium is crucial. When eggs are close to fast-moving water, they’re less likely to be fertilized.

Male angelfish will deposit sperm onto the clutch in a cloud, and heavy filters may wash this away before it makes contact. As a result, the unfertilized eggs will stay put and begin to rot.

Likewise, too-fast currents may dislodge the eggs from their nest. This could damage them or place them in a more vulnerable position in the tank, making fungus more likely to take hold. As such, be sure that the eggs are located in a safe spot. This may include:

  • On a spawning plate
  • Near plants
  • In a docile corner of the tank

Ideal Water Temperatures

For your angelfish, the aquarium water should not exceed 84 degrees F. If the water temperature rises, the oxygen levels will get lower. This heightens the chances of fungus growth and death for the unhatched eggs.

Correct Water pH Levels

If the pH levels are not properly managed, the eggs will become compromised. As they get weak, or even die, fungus will become a problem much sooner.

Angelfish are naturally found in soft, acidic water. Be sure to check which species you own and adjust the levels to their exact preferences, especially in the breeding tank.

Clean Your Tank Regularly

A well-maintained aquarium is fundamental to preventing and treating fungus on angelfish eggs. By ensuring your tank is well-balanced, clean, and properly treated, you can prevent fungal spores.