Did you find aquarium fish eggs on the side of your tank? Wondering if one morning you’ll wake up to fish, tiny aliens, or who knows what hatched in your tank? You’re not alone. Lots of fish lay eggs on glass; We’ll go through the most common culprits together, and how to deal with it.
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2. Do Fish Lay Eggs on Glass?
Yes, various kinds of fish and snails lay eggs on the glass of an aquarium. While fish themselves are diverse in color, aquarium fish eggs are usually white or translucent in the initial stage. They’re usually around 1 mm in size and they are round in shape. If you’ve ever gone to a sushi restaurant, you’ve probably seen those tiny orange dots sprinkled over the top of your house special roll: Those are roe, a kind of fish eggs.
There are many aquarium fish that lay eggs with external fertilization. Those fish can be classified into five groups: Egg-depositors, mouth-brooders, egg-burriers, nest brooders, and egg-scatterers. Once you figure out which your fish is, you can identify who laid the eggs in your fish tank. Afterward, we’ll go through the most common fish that lay eggs on the glass, and what those eggs look like.
Angelfish laying eggs on the aquarium glass decor
I’ve also tagged the types of egg layers below with info on whether or not they tend to guard their eggs, as observing your fish’s behavior can give you clues as to whose eggs they are.
Most freshwater fish fall under this category. This kind of fish scatters their eggs, sometimes using a natural adhesive. They don’t usually guard their eggs from predators, and some may even eat their own eggs.
Some examples of egg scatters are goldfish, zebra danios, tetras, barbs, and rasboras. They prefer to deposit their eggs on the gravel and plants, although it’s possible some may lay their eggs on the glass of the tank.
This classification of fish simply deposits its eggs on anything around! It may be the glass sides of the tank, aquarium glass, driftwood, crevices, aquarium decoration, plants, etc. Some egg depositors eat their eggs, while others care for them. Cichlids and some catfish are good examples of egg depositors. They do protect their eggs from predators.
c. Egg Burriers
Egg barrier species lay their eggs in dry places (like mud). The killifish is one example of an egg burrier. Since they prefer to bury their eggs (particularly in mud), they don’t lay eggs on aquarium glass.
d. Mouth Brooders
Mouth-brooders take a different approach: They carry their eggs or larvae in their mouth. The mouth-brooder can be classified into ovophiles or larvophiles.
Ovophiles lay eggs in a pit from which later, the female fish suck the eggs up into their mouth. Only a few large eggs hatch in the mouth of ovophiles.
Larvophile, on the other hand, lay their eggs on various surfaces (though not usually aquarium glass) and protect them. Once eggs are hatched, the female fish hold the fry in their mouth until they’re big enough to be released. Examples of mouth brooders include some types of cardinal fish, catfish, and cichlids.
Nest-builders form nest-like bubbles for their eggs (considered brood care, in nature). They don’t lay eggs on the glass of the tank. The most common nest-builders in home aquariums include angelfish, gourami, and betta fish.
3. What Fish Lay Eggs On The Glass of the Aquarium?
Ramshorn snail eggs on aquarium glass
Understanding which type of egg layer the fish are in your aquarium is the first step to narrowing down what’s going on with those aquarium fish eggs you found. I will also say that the most common culprit is snails: They procreate like crazy and females can lay eggs even if you don’t have a male in the tank (because they can store and release sperm later).
If you don’t have snails, other common culprits for laying eggs on the aquarium glass include: Cory catfish, royal whiptail, angelfish (nest-builder outlier), and discus. If you don’t have any of these fish, then look for any egg-depositors in your tank, like cichlids, catfish, and other bottom-feeders.
Failing that, check for egg-scatterers (goldfish, zebra danios, tetras, barbs, rasboras, etc) as while they prefer to lay their eggs on things like plant sand substrates, it’s also possible for their eggs to end up on the aquarium glass – Especially if the eggs have a a natural, sticky adhesive (like goldfish). The fish may scatter the eggs, and the aquarium flow could bring it to the glass; If there’s an adhesive, they may stick.
Cory catfish are a popular freshwater species that doesn’t guard their eggs, so they’re often a culprit that will lay the eggs on the glass and then leave them alone.
4. What Do Fish Eggs Look Like in an Aquarium?
Not all fish eggs look the same. There are various fish whose eggs are different in color, size, and shape. A few of the fish eggs are discussed below:
Goldfish eggs are transparent in color, and they look like tiny little bubbles. When the eggs of goldfish are in the process of fertilization, they turn yellow, and the center has a dark spot. The goldfish’s eggs are of a sticky texture.
When goldfish lay eggs in an aquarium, the white patch can be seen on the tank decor. Note that goldfish are considered a prolific breeder, so if you have both a male and a female in the tank, it’s bound to happen. Because they’re not a nesting species, they can lay eggs anywhere in the aquarium. Because the eggs are sticky, they will stick where they land.
Goldfish lay lots of eggs (up to 1000 at a time) and they don’t protect them. They may even eat them.
The eggs of corydoras are also transparent and white-colored. Corys lay eggs in clusters of around 10 to 20 eggs. The size of the eggs is around 1 to 2mm. Their color changes from white to brown after 1-2 days of fertilization.
Empty cory catfish eggs on glass
Like other fish mentioned, their eggs have a small black spot during the fertilization process. Corys are different from other fish in that they will readily lay their eggs against the glass sides of an aquarium.
The clownfish is a saltwater culprit that can lay eggs on the glass of an aquarium (or any decor of a tank). They usually choose a spot carefully, and clean it before depositing their eggs. They tend to prefer things like driftwood and aquarium decor, but it’s possible they will lay eggs on the glass.
Clownfish eggs in development
The eggs of the clownfish are orange in color and their size is like a small dot; They may lay anywhere from 100 to 1000. Their eggs grow quickly. Sometimes male clownfish will eat them.
Because clownfish likes to choose, clean, and prepare the egg-laying location/territory, aquarists will often add clay pots or tiles to the tank to give them a good spot to lay their eggs.
5. Eggs on the Side of Aquarium: Most Common Types
It’s very common to find cory catfish eggs, but there are a few other regulars who might have laid eggs on your aquarium glass.
a. Jack Dempsey
Jack Dempsey is a beautiful cichlid with an aggressive personality. These fish may lay large numbers of eggs (500-800) and they can reproduce frequently. Jack Dempseys prefer hard and flat surfaces for reproduction, and it will be on areas they consider their territory.
Angelfish lay very small eggs that look like white pearls, with a jelly-like consistency. Similar to goldfish, they lay LOTS of eggs. When first laid, the eggs are translucent, but they change to a brown hue during fertilization.
Angelfish may eat their own eggs if stressed and/or without enough food.
Snails are prolific reproducers and a top culprit when it comes to finding eggs on the aquarium glass. This is very common. Mystery snails/apple snails will lay their eggs just above the water line.
Snail eggs are jelly-like in texture and come in various colors from white to clear to pink.
Mystery snail eggs lay their eggs above the waterline
Some tadpole snails can be good for the fauna of an aquarium, but not more than twenty-ish. At that point, there’s usually a problem with overfeeding as snails will thrive off that free food.
Tetras are the shining jewels of many aquariums. As egg-scattered, their eggs will typically land on the substrate. If it’s a species that lays eggs with adhesive, they’ll often end up sticking to plants. Tetra eggs may be clear, white, or yellow, about 1mm in size, and round.
Discus fish are unique for their bright colors, unique body shape, and amazing patterns. Discus can lay around 400 eggs in an aquarium, ending up on various surfaces like the glass of a tank, rocks, or other decor.
Female discus may protect their eggs, but males may eat them if they’re hungry.
f. Fish That Don’t Lay Eggs On The Aquarium Glass
Egg burriers, mouth brooders, and nest-builders do not usually lay eggs on the aquarium glass. For example, betta fish (a nest-builder) don’t lay eggs on the sides of the aquarium, but instead create an air bubble with the eggs inside (30–100 at a time). There are even some bettas that are mouth brooders.
Another example of fish that are unlikely to leave eggs on the glass are plecos; They lay eggs in secure places at the bottom of the aquarium, and/or hide their eggs under the rocks. Pleco eggs are round and laid in clusters.
6. How to Get Fish Eggs Out of an Aquarium?
a. Scraping Off
A simple and helpful way to remove eggs from the fish tank is by scraping them off. You can use something thin and flexible, like a credit card (sanitized in boiling water first) to scrape them off the glass.
NOTE: If you are disposing of the eggs, PLEASE let them sit out on a paper towel and dry out first!!! This ensures that no fry will hatch. DON’T flush them down the toilet, where they can grow and hatch in terrible conditions, or end up in local waterways.
b. Use Siphon To Vacuum
Did you read that last paragraph above? Because it’s important. Okay great- Moving on:)
You can also use a siphon to vacuum up and get rid of these eggs. This is a good option to remove eggs from the glass of the tank as they won’t be able to settle elsewhere.
I recommend you always quarantine your new plant or provide your plant with a (heavily diluted) bleach dip to remove the eggs before introducing it into your tank.
7. How To Protect Fish Eggs in an Aquarium
If you want to keep the eggs, you have a few options: You can protect them by surrounding them with a divider box, separating them from the fish in the aquarium that might eat them. You can also try scraping them off and moving them to a separate fry tank for hatching. Bear in mind that if you leave them where they are without doing anything, it’s highly likely other fish will eat them.
8. Aquarium Fish Lay Eggs on Glass: FAQs
a. Should I Remove Fish Eggs From the Tank?
It’s totally up to you. If you don’t care about whether or not they hatch, you can leave them and other fish will most likely eat them, depending on who’s in the tank. If you don’t want any more fish, you can siphon them up, let them dry out, and then dispose of them. If you want to hatch them, you can remove them and put them in a separate fry tank. (Depending on whether or not there are fish in the existing. tank that would eat the fry once they hatch, this is a good idea.) If that’s the case, you can reintroduce the fry once they’re big enough to fend for themselves. Remember that parent fish can sometimes eat their young.
b. What are the eggs in my aquarium?
What creatures are living your aquarium? List them out, and go through each species to determine the likely culprit. Snails are notorious for laying eggs on the glass.
Finding eggs on the glass of the aquarium happens sometimes, especially if you have snails. Fish like cichlids and cory catfish can often lay eggs there, too. Egg-scatters who lay with a natural adhesive might have their eggs end up there, though not intentionally. Some parents will eat the eggs, others will protect them. It’s up to you what to do with them.