How Many Eggs Does A Mystery Snail Lay?

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Many fish owners are afraid that their mystery snails will lay eggs because they don’t want their tank to be overpopulated. That concern raises one central question: how many eggs do mystery snails actually lay?

Mystery snails lay between 50 and 500 eggs, of which 20 to 40 will hatch within three weeks. Their spawning season typically lasts for 4 to 5 months. During that time, mystery snails could lay eggs every couple of weeks.

As we move forward, I will elaborate on the number of eggs you should expect from your snails and discuss whether your tank is likely to get overpopulated. Fortunately, that is rarely the case.

A clutch of approximately two hundred mystery snail eggs.

Still curious? Feel free to check my complete guide on mystery snail eggs. There, I discussed how to care for the eggs, what their stages are, how to tell if they are fertilized, and much more

How Many Eggs Does A Mystery Snail Lay?

This question matters because snails can easily overwhelm your tank. To many aquarists, these creatures are pests that invade the aquarium after hitching a ride on new plants and decorations.

Don’t let their small size fool you. They will grow within a few weeks, multiplying rapidly to cover every surface in the aquarium. 

If you want to deliberately rear mystery snails, your situation is not necessarily better because these creatures can still overwhelm your tank.

A mystery snail will lay anywhere between 50 and 500 eggs in any given spawning session. They can produce multiple clusters of eggs over the course of a year.

And if you’re underprepared, the creatures will choke the aquarium. Mystery snails are too weak and dormant to threaten adult fish physically. 

However, they can kill every living thing in the tank by crowding the water, creating oxygen deficiencies, and increasing the ammonia concentration. 

You can’t control their mating habits by simply removing the male snails. After all, female snails can store sperm for 140 days or more.[1]

This allows the creatures to fertilize their eggs whenever they wish, producing healthy offspring in the absence of a male snail.

How Many Snails Come From Mystery Snail Eggs?

Knowing the number of eggs a mystery snail can lay is only half of the equation. It doesn’t tell quite as much as you expect. 

If a mystery snail can lay as many as 500 eggs, how come many ordinary aquarists raise mystery snails without running out of room? Indeed, a mystery snail can overrun a conventional aquarium within a year. 

First of all, aquarists do not keep all the eggs their snails produce. They will hatch the number their tank can accommodate before killing or donating the rest. 

Secondly, a clutch of eggs typically generates 20-40 snails, hatching within two to three weeks.[2] Mystery snail eggs cannot hatch unless a male snail fertilizes them. But you can’t expect these creatures to fertilize every egg the female produces.

Some eggs will rot because of infertility. Others will hatch, but the baby snails will die before attaining adulthood. Some aquarists will lose their entire cluster of eggs.

Don’t forget that mystery snails lay eggs above the waterline.[3] The species has gills and lungs, but they can’t breathe under water. Therefore, if a cluster falls into the water, you will lose all your eggs because the embryos drowned.

Fortunately, mystery snails will generate multiple clusters of eggs per year. Therefore, if you’re determined to raise mystery snails, you don’t have to despair because you lost all the eggs. The breeding pair will generate more offspring.

It is worth noting that the conditions in the aquarium affect the number of eggs a mystery snail produces, not to mention the number that hatch. 

A paper exploring breeding patterns among apple snails found that temperature and light intensity influenced egg production and the growth rate.

Published by A Santos-Soto and A.O. Meyer-Willerer, the study exposed female snails and their eggs to various temperatures and light intensities. It found that warm temperatures boosted hatching efficiency.[4]

For that reason, professionals encourage newcomers to maintain a temperature of 76 to 82 degrees F. High air humidity is just as critical. 

Moisture is important. The cluster must remain moist, which is why mystery snails attach the eggs to the wall above the waterline. You can move them to a safer location if the cluster is coming unstuck.

However, mystery snail eggs are fragile during the first two days. Therefore, you may destroy the cluster by trying to move it. You are better off waiting a few more days for the eggs to harden.

If you can move the eggs, place them on a damp towel in a container with a lid to increase their chances of successfully hatching. 

You should check on the eggs routinely. Observe the changes. Again, some eggs will die because of infertility, genetic anomalies, or poor conditions. Dead eggs are easy to spot because they have a terrible smell.

You should dispose of them as soon as possible, especially if the eggs fell in the water. You don’t want the decomposition process to raise the ammonia concentration.

One-week-old mystery snail eggs attached to a home aquarium.

How Often Do Mystery Snails Lay Eggs?

Snails are fascinating because their breeding habits are so diverse. Some species reproduce once (Pulmonate Snails). Others will spawn multiple times a year.[5]

With mystery snails, you can expect new eggs each week. But this spawning behavior will only persist for 4-5 months.

These creatures are self-sustaining. If you leave them alone, they can add an average of 20 to 40 babies to the aquarium.

Admittedly, you cannot always predict a mystery snail’s spawning activities. Some female snails will lay eggs every week, while others may only lay eggs once or twice a month.[6]

The conditions in the tank matter. How much food do the creatures have? You don’t have to feed the snails directly if they have plenty of detritus in the water. However, some aquarists will remove the algae and dead leaves to limit food accessibility.

They will also perform frequent water changes because they want to make the aquarium less conducive for breeding snails.

If they have fish in the tank, they will reduce the meal sizes to cut the volume of leftovers. Interestingly, many aquarists use snails to eliminate leftovers and algae. 

Removing these food sources will discourage the creatures from breeding. This assumes that you want to prevent breeding. If you’re objective is to increase the number of spawning sessions, you can raise the temperature and lower the waterline.

How Long Does It Take For A Mystery Snail To Lay Eggs?

Mystery snails will lay a cluster of eggs within ten days. Some female snails will seemingly lay eggs within a day or two of mating with a male snail. But you have to remember that female snails store sperm.

They can use that sperm to fertilize their eggs. Therefore, a female snail can lay eggs fertilized with sperm acquired at the fish store before you bought it. This can easily confuse your calculations and estimates regarding the mystery snail’s incubation period. 

Will Mystery Snail Eggs Overpopulate My Tank?

Many aquarists get worried when they hear that mystery snails can produce hundreds of eggs. Even though many of them won’t hatch, even a batch of 20 to 40 snails can be overwhelming.

Fortunately, mystery snail eggs are easy to identify. You’ll see a noticeable clutch hanging on one of your aquarium’s walls. If you don’t want baby snails, simply remove them from your tank.

If you’re interested, here is an article where I discussed what you could do with mystery snail eggs. I explained what steps you should take if you wish to raise them but also mentioned the alternatives.

Either way, it isn’t likely that the babies will catch you by surprise. You’ve got a few weeks to prepare (approximately two to three weeks).

You can also use these eggs to feed your fish. Baby snails are highly nutritious. Some fish owners even grow them for the purpose of feeding their fish.

All you have to do is to wait until the eggs darken. That will indicate that they are fertilized. Then, simply place them under the waterline. The eggs won’t be able to hatch there, and your fish will enjoy a healthy meal.

If you go with that method, it is essential to see whether some of the eggs are being neglected. If your fish don’t eat them, the eggs will rot and contaminate your tank. Wait a couple of days and take these eggs out of the water.

To find out whether the eggs ruined your water, simply get a test kit. I personally use the API FRESHWATER MASTER TEST KIT (link to Amazon). The ammonia and nitrite should be at 0 ppm. If they are higher than that, search for uneaten eggs and perform a water change.

An excellent Youtube video that explains how to hatch mystery snail eggs.

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If you grow mystery snails and worry about their eggs and overpopulation, you shouldn’t get too hung up on it. Even though these snails can lay hundreds of eggs, only a small percentage will eventually hatch.

The rest of the eggs are usually not fertilized. In some cases, the baby snails die inside for numerous reasons. Either way, time is on your side.

Once you find a clutch of mystery snail eggs, you have about three weeks before they hatch. During that time, you can choose to get rid of those. Many aquarists use them to feed their fish, so they don’t go to waste.