How to Tell if Mystery Snail Eggs Are Fertile

Last Updated on April 6, 2022 by cmoarz

Mystery snails are able to produce and lay infertile clutches of eggs if they haven’t mated. What makes this entire process more complicating is a snail may mate, and then only lay the eggs far into the future. Unlike many other snail species, a mystery snail can not reproduce asexually.

So it’s always a guessing game whether the eggs are fertilized or not. Luckily it’s easy to tell if mystery snail eggs are fertile with just a quick glance.

Check out our identification guide What does snail eggs look like To help identify more snail eggs

How to tell if mystery snail eggs are fertile

A fertilized egg with a tiny developing snail in it should have what looks like a little black spot in the middle of the egg. The eggs will look larger and “fuller” with more irregular shaping. The color of the eggs will start to vary as time goes on, showing that they are indeed alive. Dark and light-colored eggs initially just mean moisture content.

You may notice some white developing on some of the eggs. Sometimes this means a fertile egg has died, However, It also means they might be getting ready to hatch. Your eggs may look moldy just before the time comes for the baby snails to break free. This is normal, do not panic. This is caused by the snails slowly eating their way out and the egg sack will become thinner because of this, causing this appearance.

Protecting Fertile Eggs

If your eggs are fertile, you will need to decide if you want to remove them from your aquarium and place them in their own holding tank, Or on a damp paper towel. Remember to mist them every day.

While it’s not necisary to remove the eggs from the original tank, it comes down to your own unique circumstances. Small snails are vulnerable to many species of fish, bottom feeders and shrimp.

If you think there’s anything in your tank that might threaten the survival of the baby snails, it’s best to remove them to their own tank until they are large enough to no longer be prey.

A good alternative to this would be a breeder box. If you don’t have one you should pick one up. Not only are they very affordable (10$ give or take in most cases), They will make your life considerably easier.

A breeder box will protect the fertile eggs as well as the baby snails until they are big enough to be off the prey list. It also makes a good containment room in case you plan on moving the snails at a later date. Nothing worse than trying to collect 50+ baby snails that blend into the gravel from a tank. Definitely get a breeder box.

How to tell if mystery snail eggs are Infertile

Infertile eggs will all look very uniform, and small. There will be no black spots and they will be fairly dark in color. After a week or 2, they will start to put off a unique odor which will be your defacto signal these eggs are infertile.

If you put your eggs on a damp paper towel in order to hatch them outside of the tank, You will notice infertile eggs will stain the wet paper towel with a red substance. Fertile eggs won’t do this!

Another more obvious sign your eggs are infertile is if you don’t even have a male. Sexing Mystery snails go beyond this article, however. A good rule of thumb is if you have more than a handful of snails in a tank, it’s almost a guarantee they are fertile. If you only have a few, then it’s a 50 / 50 shot. Remember, at the beginning of the article we said mystery snails cannot reproduce asexually.

So, do mystery snails lay unfertilized eggs? They absolutely do! Although they will retain fertilized genetic material for up to 140 days after being with a male snail.

Disposing of Fertile and Infertile Eggs

If for some reason you find yourself needing to dispose of good fertile eggs, Or just to remove some dead infertile eggs, The procedure is the same.

Ye’ old crush and flush.

Yes, it sounds terrible! To us keepers, snails beautiful creatures that deserve life and freedom. They are absolutely stunning in color and life. Unfortunately, the rest of the world doesn’t see it the way we do.

The sad reality is, snails are pests. They destroy crops, vegetation, and ecosystems. That’s why land snails are illegal in the United States and Canada. Those big boys could destroy everything.

Even though mystery snails are much smaller, it is still our responsibility as aquarium snail hobbyists to deal with these eggs in a proper manner, as cruel as it might seem.

Method 1, Crush Them

The first method is the cruelest in our opinion, but also very effective. Simply place the fertile or infertile eggs between some paper towels and start crushing the eggs with your foot or something heavy. Then flush them down the toilet or throw them in the trash.

Why do we take such precautions with infertile eggs? It’s better safe than sorry. Even if an entire clutch seems infertile theirs always a possibility some are not.

Method 2, Freeze the Eggs

This method might be easier for some of you to manage without feeling so terrible. Simply place the eggs in the paper towel like the first method, but place them in the freezer for a few days instead.

Then dispose of them in the same manner, Either by flushing them down the toilet or disposing them into the trash.

The act of freezing will make quick work of the eggs and is considered a more humane method of execution. This is also how we deal with baby mice bred for snake food (I know! D:). Luckily that’s something my family does, not me!

Bottom line

Seeing if a mystery snail egg clutch is alive and well is fairly easy. Just look at the signs in this article. Black spots, irregular shaping, etc.

Remember that it is YOUR DUTY as a qualified and responsible aquarium hobbyist to dispose of any unwanted eggs in a proper manner and to not let them escape into the environment. Even if you think they are dead or infertile!

How to Hatch Mystery Snail Eggs

The first thing you’ll want to do is find a still, clean, and safe area that can be used as a hatchery. A plastic container would be good for this. Place some damp paper towels in the bottom of the container and make sure they are large enough to cover the eggs once placed on top.

Float the container inside the aquarium that you want the eggs to hatch in. I use a small fish aquarium as my hatchery. This allows the eggs to stay warm from the ambient heat from the aquarium water.

It also allows them easy access to the tank once they hatch.

It takes between 3-4 weeks to hatch a mystery snail egg. If the eggs are fertilized you should see some signs of development within this time.

Once hatched, the baby snails will climb out of their container. One thing to consider is, just before they are ready to hatch, placing them into a semi-submersible hatching container inside the aquarium itself.

This way they can get into the water while also staying safe and easy to spot. Snails are basically the size of a pinhead when they are born and it’s much easier to keep track and feed them when they are all in 1 spot.

This will also keep them from getting sucked up into the filter.

How Can You Stop Mystery Snails from Breeding?

Breeding is a mystery snail’s favorite pastime. It is the main reason these pests are growing so quickly and are now an invasive species throughout the world. If you have mystery snails, you may be noticing that populations seem to be increasing at an increasingly faster rate.

The effects of breeding on your precious aquarium ecosystem should not be underestimated, it can turn your tank into a slimy mess of bacteria and algae within a few month’s time. Completely throwing off the sensitive balance. Fortunately, there are several things you can do to stop them from breeding and putting your aquatic life at risk.

First, Raise the waterline and make it difficult for them to lay their eggs. They will lay less often if they can’t find an ideal place to lay.

Lowering the temperature will also slow them down. Mystery snails are more active in warmer temperatures and will lay eggs more often when it’s higher.

Keep their population under control by removing the excess eggs when you see them.

Feeding them less food will lower their egg production, consider changing their meal plan a bit.

How to take proper care of baby Mystery snails after the hatching?

Once your mystery snail eggs have been hatched, you need to take care of the babies. You want to make sure that they are fed properly with a healthy diet and given the right temperature that is suitable for them. This will help keep them alive and also ensure their health as they grow larger.

They eat the same things adults do include algae, fish food flakes, fresh vegetables, shrimp pellets (without copper sulfate) among other things. Don’t rely on algae alone.

As they grow bigger, they will need to be supplied with larger food sources that are more suitable for their size.

Keeping water parameters constant is the trick to helping them grow beautiful shells. If water params change too often, it will cause ugly growth rings in their shells. Make sure to always do a water test before you add anything into your tank that may change the numbers.

If pH is off or hardness is too low, it will cause shell growth problems. Consider adding cuddle bones or powdered calcium to the water to increase the hardness and calcium ppm. Overall calcium for a mystery snail is super easy to deal with supplementary. It’s important to keep it in the water and high in the foods they eat.

If water is too acidic, it will damage and slowly eat away at their shell.


Owner of and also owner of actual Aquarium Gravel believe it or not! ;). Setting up beautiful aquarium sceneries and habitats since I was very young. Enjoy!