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How Many Mystery Snails Per Gallon Freshwater?

How Many Mystery Snails Per Gallon Freshwater?

Image Credit: Creative Common on Flickr

You might have read how the mystery snail population grows exponentially within weeks in forums. I know hobbyists whose mystery snail population doubled within months. They are fed up squandering on a tank upgrade every 3 months. 

It isn’t wrong in any sense to get a new tank for your pets but purchasing a new tank every 3 months isn’t always viable unless you are planning to breed and sell them.

So, how do you know how many mystery snails can you keep per gallon and how to tell if you have too many of them?

Let’s find out.

How Many Mystery Snails Per Gallon Freshwater?

You can keep up to 2 mystery snails in a 5-gallon tank. Use this simple formula: Divide the tank capacity in gallons by 2.5, and you will know the maximum number of mystery snails you can keep. 

For example: If you have a 30-gallon tank, you divide it by 2.5, which gives you 12. This means you can keep up to 12 mystery snails in a 30-gallon tank.

But, what if you have to know how much water a mystery snail requires?

Referencing the ratio of 2 mystery snails per 5 gallons, a single mystery snail will need at least a 2.5-gallon tank. 

Voila! The formula got even simpler now. 

No.of mystery snails X 2.5 = Ideal tank size

Let’s put the formula into action.

Suppose you want to keep 10 snails; what tank size will be the appropriate one?

Using the above formula, 

10 mystery snails X 2.5 gallons = 25-gallon tank

The following method is the same one I applied right at the beginning. I am only revising it in case you are confused. 

Suppose you have a 40-gallon tank, and you plan to add only mystery snails to it. How many of them can you keep without harming the tank’s nitrogen cycle?

Let me put on my geeking hat.

Tank size divided by 2.5 = Maximum number of mystery snails

40 divided by 2.5 = 16

Hence, you can keep 16 mystery snails in a 40-gallon tank at a given time. 

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What Other Factors Should You Consider Before Getting A Tank For Your Mystery Snails?

Although the formulae I mentioned earlier are flawless, there are still several factors that you have to take into consideration before getting a new tank for your snails. 

Let’s dive deeper.

Main Purpose 

The number of mystery snails that you keep also depends on the purpose behind it. If you just want to control the algae growth in your fish tank, you don’t need a horde of mystery snails. A couple of them will do. 

But if you do not have any biofilm or algae-producing ecosystem in your tank, it’s better not to keep these snails at all. 

Did you know that mystery snails do not eat fish poop? So, don’t assume your mystery snails will keep the tank squeaky clean and declare it a poop-free zone. 

Size Of The Tank

This is an obvious factor to consider before getting your first batch of mystery snails. At a minimum, you will need a 2.5-gallon tank for a single mystery snail. So, plan accordingly. 


I have seen beginner aquarists buying smaller tanks to cut their expenses. However, this is a bad idea in retrospect. The smaller the tank, the harder it is to maintain correct water parameters.

Therefore, a mid-sized tank is what you should invest in if you are testing the waters for the first time. 

It’s not small enough to not offer any room for errors but also not big enough to be overwhelmingly difficult to manage. 

And a good thing about mid-sized tanks is that you won’t need to break the bank to afford one. To estimate, a 20-gallon tank comes under $150. 

Here’s a 20-gallon tank that I use for keeping my freshwater snails. The best thing about a mid-sized tank is that you can turn it into a community tank, too. 

Care And Maintenance

You may have heard how tough mystery snails are. But that doesn’t mean you toss a bunch of them in your tank and leave them to their own devices.

That’s not what I’d recommend you should do. 

These snails do need attention. You should regularly check water parameters and provide a balanced diet along with calcium supplements. 

Assuming they will survive on algae alone is not the way forward.

These snails are avid algae-feeders and will finish the tank’s algae reserve within weeks. They will devour it even faster if allowed to reproduce in the tank. 

So, you will need to dedicate more time and effort to keep one too many mystery snails. 

Let’s talk about a mystery snail’s ability to resist incorrect water parameters. 

There’s no doubt that mystery snails are hardy and can tolerate fluctuating water parameters. And what’s even more surprising is that research shows snails living in biofilms and bacteria-infested tanks are more likely to thrive than snails kept in clean waters. 

But how dirty is dirty enough?

It might sound contradicting, but I suggest you keep only a couple of mystery snails if you want your tank to be self-reliant in algae production. 

The Tankmates

If you keep your mystery snails in a community tank, make sure there are no predators to devour them. 

Mystery snails have a calm temperament, so you need to keep them with other placid creatures. 

Ordinarily, fish do not bother mystery snails. However, they can get territorial if snails intrude and disturb their privacy. 

How To Control Mystery Snail Population In The Tank?

If your tank is experiencing rapid mystery snail population growth, it is time that you find a solution for it. Try keeping males only, or add assassin snails to halt their uprise. 

If there’s too much infestation, you can resort to using molluscicides to eradicate them all. 

Let me brief these methods to control the mystery snail population further.

Keep Males Only

Unlike most freshwater snails, mystery snails aren’t hermaphrodites. Instead, they have distinct sexes – male and female. 

Did you know that female mystery snails can hold sperm for more than 9 months? 

So, if your mystery snail lays eggs even in the absence of a male in the tank, don’t be surprised. 

Furthermore, they cannot reproduce asexually. So, all you have to do is get only males. But this tip is more of a preventive measure than the actual treatment you seek. 

Remove Them Manually

Removing mystery snails manually is an effective way to control their population boom.

They can repopulate at a rate of knots. 

So, removing manually only works if you commit to doing it regularly. While removing snails, try scraping their eggs, too. 

And after you are done picking snails for the day, wash your hands properly. Snails harbor all sorts of pathogens in their body. And you definitely don’t want to contract them. 

Add Killers In Your Tank

If you do not want to spend your Sunday mornings picking snails, it is time for assassin snails to make their debut. 

Assassin snails will happily dine on mystery snails. 

And if you like to explore other options, you can keep botia loaches, dwarf puffers, clownfish, yoyo, or skunk loaches. 

Use Chemical Only As A Desperate Remedy

This isn’t something I’d recommend. A healthy number of snails benefits the tank by aerating the substrate, cleaning algae, and feeding on carrions. 

Adding chemicals will annihilate your entire cleaning crew.

However, if you have reached the point where your snails have made your tank inhospitable, you can resort to using chemicals. 

Carefully do your homework before zeroing in on any chemical, and beware of the repercussions you face. 

Not all chemicals are safe for fish and shrimps. So, you need to read the product description thoroughly before buying. 

Here’s a snail treatment that is safe for both fishes and shrimps. 

However, this will not work for removing eggs. 

Perhaps, the chemicals have no effect on the snails’ eggs due to their shells. 


How Many Mystery Snails In A 20-Gallon Tank?

A 20-gallon tank can house 8 mystery snails without detrimental effects on the nitrogen cycle. But if it is a community tank, you can keep about 5 mystery snails.

How Many Mystery Snails In A 30-Gallon Tank?

A 30-gallon tank falls under the mid-sized category and can accommodate about 8 to 12 mystery snails. It will be enough to create a habitat that can produce enough algae for your snails. 

How Many Mystery Snails In A 5-Gallon Tank?

At maximum, you can only keep 2 mystery snails in a 5-gallon tank. Therefore, I recommend only keeping males in such a small space. 

How Many Mystery Snails In A 3-Gallon Tank?

A 3-gallon tank will not produce algae for more than one mystery snail. So, if you want to keep two or more, I suggest getting a bigger tank.

Final Words: How Many Mystery Snails Per Gallon Freshwater?

Some hobbyists do not bother counting the number of snails in their tank. They only heed later when they notice a foul smell coming out of their tank as the snails keep dying rapidly from malnutrition and ammonia spikes. A day late and a dollar short. 

Try the formulae I mentioned at the beginning to get an accurate estimation of how many mystery snails you can keep per gallon. 

Don’t worry, folks. It is not rocket science.

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How Many Snails In A 10-Gallon Tank?

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