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How Many Snails In A 20-Gallon Tank?

How Many Snails In A 20-Gallon Tank?

It can be a knotty problem for every beginner in this hobby deciding which tank size will be perfect for lodging their slimy friends. 

And what does our basic instinct (convenience) tell us? Go for the smallest tank. We believe it will be the easiest to maintain. 

But let me tell you the truth. Small tanks aren’t easy to maintain. This is why, sometimes, gut feelings can put you wide of the mark. 

I always recommend my fellow readers to go for a medium-sized tank with at least the capacity to hold a batch of their favorite snails. 

I like medium-sized tanks that are no less than 10-gallons. So, I would suggest novice hobbyists go for a 20-gallon tank. 

Before I tell you my reasons, let’s discuss how many snails you can fit in this mid-sized tank.

How Many Snails In A 20-Gallon Tank?

As per the favored estimation method, “one inch per gallon,” you can keep about 20 snails in a 20-gallon tank. However, this only applies to snails that reach 1 or 1.5 inches at max. As for the bigger snails that can grow more than 2 inches, you can only keep 12 to 15 of them. 

In my 10-gallon tank article, I mentioned that you can only keep 2 to 5 snails in a 10-gallon tank. And if we use the same ratio that I explained there, it hints that a 20-gallon tank will be enough to hold 10 snails. 

However, the snail’s size is only one variable in this equation. While predicting the number of snails to house in a tank, we also have to take the tank’s surface area, the number of rocks, and their sizes, vegetation, and decorations into account.

This time, go with your gut feeling. 

List of snails that are below 2 inches in diameter:

  • Zebra nerite snails (Neritina natalensis)
  • Tiger nerite snails (Vittina semiconica)
  • Horned nerite snails (Clithon corona/diadema)
  • Ramshorn snails (Planorbidae)

List of snails that can grow beyond 2 inches in diameter

  • Mystery snails (Pomacea bridgesii)
  • Japanese trapdoor snails (Cipangopaludina japonica)
  • Rabbit snails (Tylomelania)
  • Black devil snails (Faunus ater)
  • Apple snails (Ampullariidae)
  • Pond snails

Now that you have the idea of how many of these species you should keep in a 20-gallon tank, let me tell you why I think that a 20-gallon tank is perfect for beginner snail keepers.

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Benefits Of Having A 20-Gallon Snail Tank

There are several advantages of getting a 20-gallon tank for snails. I will list them down below:

  • Versatility
  • Preferred for both beginner and advanced hobbyists
  • Economical
  • Serves purposes like breeding and quarantining
  • Easy Maintenance


A 20-gallon tank is a versatile tank. You can mold it into making a snail-only habitat, or you can add other tankmates and make it a community tank. 

The large surface area gives you more opportunity to add even bigger tankmates like the cichlids or a school of rasboras.

Furthermore, you can stack double or triple tanks on top of each other. But remember that they should be a 20-gallon long tank, not a 20-gallon tall tank.


I consider it an economic tank because you can get it for under a hundred bucks. 

Also, it is commonly available, making the availability of additional parts like the lids or dividers widespread. The filter you use for a 10-gallon tank will also suffice for this sized tank. 


The perk of getting a mid-sized tank is that you don’t have to spend hours changing water. You only need to change 5 gallons of water in a week. Commit 15 minutes, and you are free to do your other chores. 

You will only find yourself too involved with this sized tank if you clean it in a leisurely fashion or mess up the tank’s architecture. 


An empty 20-gallon tank weighs about 25 lbs. So, even if you are raw-boned like me, you can carry this tank to your desired destination easily. 

When filled with water, substrate, plants, and decors, it weighs about 225 lbs. If you have sturdy furniture lying around that can bear that much load, you do not need to spend extra bucks for a dedicated stand. 

Other Uses

This tank can serve as an excellent quarantine tank, too. Usually, sellers recommend quarantining your snails for at least a month or two to prevent disease breakout. 

So, to isolate snails for that long, a 20-gallon tank suits perfectly. It is large and can accommodate hordes of snails. 

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How To Acclimate Snails In Freshwater? What Happens If You Don’t Acclimate?

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Best Snails To Keep In A 20-Gallon Tank

Here are some snails that you can keep in a 20-gallon tank:

  • Nerite Snails
  • Zebra nerite snails
  • Horned nerite snails
  • Tiger nerite snails
  • Mystery snails
  • Assassin snails
  • Japanese Trapdoor snails
  • Rabbit Snails
  • Black Devil Snails
  • Malaysian Trumpet snails


How Many Mystery Snails In A 20-Gallon Tank?

Mystery snails grow 2 inches or more in diameter. This means you cannot apply the “an inch per gallon” rule here. So, you can house about 12 to 15 mystery snails in a 20-gallon tank.

How Many Nerite Snails In A 20-Gallon Tank?

Most nerite snails fall on the smaller side, reaching only about a size of a quarter at max, i.e., 1 inch in diameter. So you can put 20 of them in a 20-gallon tank without affecting the tank’s nitrogen cycle. 

How Many Ramshorn Snails In A 20-Gallon Tank?

Ramshorns are fast-breeding snail species that grow up to 1.5 inches in diameter. Some are even smaller than that. Due to their fun size, you can have room for 20 to 25 of them in a 20-gallon tank.

How Many Land Snails In A 20-Gallon Tank?

A well-fed healthy land snail can reach 8 inches in shell diameter. So, even a group of adult land snails (6 to 7) can make your 20-gallon tank look crowded. Therefore, I recommend keeping only one or two couples. 

How Many Assassin Snails In A 20-Gallon Tank?

Late bloomers, assassin snails, reach only about an inch in shell diameter. But there are accounts of them reaching up to 3 inches, too. Therefore, putting 15 to 20 of them in a 20-gallon tank is better. I recommend staying in the lower range (just in case). 

Final Words: How Many Snails In A 20-Gallon Tank?

The answer to this question in real is: It depends. Factors like the species, size, grazing surface area, tank mates, rock, and decor sizes must also be acknowledged before stabbing in the dark. 

An inch per gallon rule isn’t applicable on all occasions. It only applies to snails less than 2 inches in shell diameter. And for the larger ones, you have to put on the thinking cap and pragmatize all the abovementioned factors. 

Personally, I like a 20-gallon gallon tank for my snails and smaller fish breeds. It is easier to maintain, lighter to carry, and purposeful for every beginner to advanced aquarists.

Relevant Readings:

How Do Freshwater Snails Kill Humans?

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How To Tell If Mystery Snail Eggs Are Fertile?