Jelly-Like Substance In Fish Tanks: What Is It & How To Remove It

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Many aquarists wake up one day to find their tank infested with a strange jelly-like substance.

This material may appear in different colors, the most common being white and pink. When I first found it, I had no idea what it was or what to do.

But after extensive research, I came up with some answers. And to make life easier for you, I decided to collect all the essential information in one article.

What Is The Jelly Substance In My Fish Tank?

The white jelly-like substance found in fish tanks could be snail eggs, which are usually attached to plants or the aquarium walls, or it could be fungus or biofilm caused by decomposing organic matter in the tank.

1. Snail Eggs

Where did you find the white jelly-like substance? On the leaves of your plants? Or is it attached to the walls of the aquarium? Most likely, you are dealing with snail eggs. 

Snail eggs confound amateur aquarists with conventional fish tanks because they only expect snail eggs to appear when they breed snails.

Therefore, if you don’t recall buying snails from the local fish store, you might be hesitant to classify the white jelly-like substance as snail eggs. 

Try to keep the following in mind:

  • Where Do They Come From?

You get eggs when snails breed. Some snails reproduce sexually. Others reproduce asexually. 

Regardless of the method, you typically get new snails when their offspring hatch from eggs. However, snail eggs can also hitch a ride on new additions to the tank.

That would include plants, decorations, and even the substrate and filter media if you sourced them from an established tank. 

  • What Do Snail Eggs Look Like?

That jelly-like substance is a dead giveaway. Snails lay eggs in clutches. A transparent sac keeps them together.

You may confuse them for bubbles, at least initially. But that will change once the fertilized eggs mature. 

Their color is the most distinct feature. It will change over the days and weeks. Look for dark spots. Unfertilized eggs will remain the same. 

Don’t wait for them to develop a rotten smell before removing them. Eggs produce toxins like ammonia when they rot. The snail type will influence the egg’s appearance. 

For instance, apple snails produce pinkish clusters and the same goes for mystery snail eggs. Ramshorn eggs are jelly-like sacs with clear or white dots. 

If you’ve noticed individual eggs in a crevice, they came from an assassin snail. Bladder snails are similar to their ramshorn counterparts. The eggs exist inside a clear goo.

Eggs that were recently laid on a leaf (these eggs are fertilized).
  • Where Do I Find Them?

Apple snails will attach their eggs to an object, such as the tank wall above the waterline.[1]

But you should also check the underside of a leaf, decorations, and substrate. Don’t limit your search to the top of the substrate.

If the eggs enter your tank via gravel from an established tank, they are mixed in with the substrate. You need a vacuum to find them.

If the eggs came from a live snail that snuck into the tank, you have a more significant issue on your hands. 

For instance, apple snails can add eggs to your tank every seven days. 

Pomacea maculata produces clutches with as many as 2000 eggs.[2] What sounds like an inconvenience could devolve into a full-blown infestation.

  • Are Snail Eggs Dangerous?

On the surface, snail eggs are not dangerous. But naturally, you have exceptions.

A paper in Malacologia (Horacio Heras, Enrique L. Portiansky, Tabata R. Brola, Patricia E. Fernandez, Marcos S. Dreon) identified apple snails as one of the worst invasive species in the world.[3]

Therefore, you could wreak havoc on your environment by flushing apple snail eggs down the toilet. 

If you don’t mind leaving the apple snail eggs in the tank, apple snail eggs generate a toxin with antidigestive properties that repel predators.[4]

This is a problem because fish eat anything that fits in their mouths; unfortunately, apple snail eggs can fit in a fish’s mouth.

Excluding the cases above, snail eggs are harmless unless you permit them to rot. Rotten eggs will ruin the water.

  • What Should I Do About It?

If you like snails, let the eggs hatch. The tank cleaners will eat the algae and detritus they encounter in the water.

If you don’t want snails, use species such as loaches and puffers to eliminate the eggs. Even if they hatch, the loaches will eat the babies.

Baby snails and their eggs are a decent protein source for your fish. If the fish refuse to eat the eggs, scrape the clusters off walls, decorations, leaves, and filters.

Place them in a bag in the freezer. The goal is to make sure the eggs won’t hatch before you throw them away. You have two weeks to make a decision. 

Otherwise, the eggs will hatch. Then again, even if the eggs hatch before you act, you can still euthanize and dispose of the snails. 

Use gloves before handling the snails and their eggs. 

According to the Centers for Disease Control, freshwater snails can cause schistosomiasis in humans.[5]

The disease, which originates from a parasite, afflicts 250 million people worldwide.[6] Also, don’t forget to dip new ornaments in a bleach solution. 

With live plants, hydrogen peroxide solutions will remove foreign organisms, including snails.

Your local store cannot guarantee that the decorations and plants you buy from them are snail and egg free.

2. Fungus

Every aquarium has fungi because they thrive in environments with decomposing organic matter.

And unfortunately, you can’t keep decomposing organic matter out of a tank. The more fish you have, the more fungus you will attract.

  • What Is It Actually?

Fungi are single or multicellular organisms that appear in every habitat you can imagine, including fresh and saltwater bodies and soil.[7]

If you routinely confuse fungi with algae, just remember that algae are capable of photosynthesis. They are comparable to plants. 

  • What Causes Fungi?

Fungi are drawn to decomposing organic matter. The following factors will encourage their growth:

  1. You don’t have a filter, or the filter is too weak to keep the water clean.
  2. You routinely overfeed the fish, producing more waste and leftovers in the process.
  3. The tank is too small or overcrowded, which allows the ammonia and nitrate concentration to spike.
  4. You don’t change the water.
  5. You allow dead fish and plants to remain in the aquarium. 
  • Where Are They Usually Found?

The fungus will cling to every surface it can find. Check the accessories, including the plants, filters, and ornaments. 

You should also check the base and sides of the tank. Some people introduce fungi by adding infested objects such as driftwood.

In other cases, fungi grow on new ornaments like driftwood because they have some decomposing organic matter. 

Look for a slimy, translucent substance that grows on or around the waste matter. Most people describe it as a fuzzy, cotton-like growth.

  • How Do I Remove Fungus?

If you want to get rid of the fungus in your fish tank, here’s what you need to do:

  1. Remove the infested ornaments and scrub them.
  2. Clean the tank. That includes scrubbing the walls and vacuuming the substrate.
  3. Perform frequent water changes.
  4. Remove fish waste, leftovers, and dead organisms before they rot. 
  5. Apply antifungal treatments such as API PIMAFIX (link to Amazon). Check the ingredients and warnings. 

Make sure the anti-fungal product is safe for your aquarium’s inhabitants. Anti-fungal treatments with toxic elements have manuals that warn consumers. 

You can still use the treatment. But you should move the fish to a second tank before you proceed.

3. Biofilm

While many people describe biofilm as a white slime, some may see it as a white jelly-like substance. It’s just semantics.

A biofilm is a clump of different bacteria that hold together using a clear slime to cling to surfaces. You may see it on driftwood, leaves, rocks, etc.

As with fungi, biofilms usually form in unmaintained tanks rich in nitrogenous waste, with ammonia in particular.

Therefore, this material can be disposed of by following the same steps as above, starting with routine maintenance and aquarium cleaning.

It is equally important to vacuum the substrate, as this area usually contains a lot of debris and fish waste.

You can easily do this with the Hygger Aquarium Gravel Cleaner (link to Amazon). It is quite cheap and easy to use. Use this device once a week.

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If you find a clutch of round, jelly-like materials, you’re probably dealing with snail eggs. This is quite common and you don’t need to worry about it.

Obviously, there must be snails in the tank for this option to be viable. If not, the next best guess is fungi, which many times resemble white cotton-like spots.

You may also be dealing with a newly formed biofilm. This material is more slimy and consolidated and often appears on driftwood and rocks.