How Many Neon Tetras Can Fit in a 20 Gallon Tank?




how many neon tetras in a 20 gallon tank

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Neon tetras are a piece of the puzzle when it comes to stocking a 20-gallon aquarium. How many neon tetras can you put in a 20-gallon tank? The answer largely depends on the other fish in the tank and the maximum size and personality of the neon tetras.

In general, a good rule of thumb is to stock one inch of fish per gallon of water. This means that a 20-gallon tank could theoretically hold 20 neon tetras. However, this is not always the best option, as neon tetras are small and need space to swim and hide.

But don’t worry, I’ve got all the answers to your burning neon tetra questions from personal experience. How many neon tetras can live in a 20-gallon aquarium? How do they interact with other fish? What do they like to eat? Keep reading to find out!

How Many Neon Tetras Can I Put in a 20-Gallon Aquarium?

A 20-gallon tank can support anywhere from 10 to 30 neon tetras. I realize the range is broad, but let me try to shed some light on it. 10 is a safe start for a beginner fishkeeper. However, if you’re an experienced fishkeeper comfortable with overcrowding, 30 is perfectly feasible.

Also, the stocking number for your tetras depends on your tank type. For example, a 20-gallon long tank can accommodate more neons than a 20-gallon high tank because it has a larger surface area.

To determine the number of fish to stock, hobbyists adhere to a few regulations. Two examples are the argumentative “one inch per gallon” rule and the more forgiving “12 square inches of surface area for every inch of body length”.

So, what would the stocking numbers look like if we applied these standards? Let’s take a look!

The 1 Inch Per Gallon Rule

As I mentioned, the one-inch-per-gallon rule is debatable in fishkeeping. This is because it overlooks the fish’s height, weight, and activity level.

However, you can apply this rule to only fish smaller than 3 inches. This rule will create an overstocked, stressful tank environment for larger fish. Imagine being crammed into a tiny room with 30 other people – not fun, right?

This rule also doesn’t consider the different types of fish tanks. A 20-gallon high tank has less surface area than a 20-gallon long tank and can support fewer fish.

Generally, neon tetras grow to be 1.5 inches (4 cm) long, but for the purposes of this equation, we will assume they are 1.75 inches (4.45 cm).

Therefore, a 20-gallon tank could comfortably hold 11.42 (20/1.75) tetras. You can either round that number up to 12 or 11 when stocking your aquarium.

The 12 Square Inches for Every Inch Rule

In his well-known book, You and Your Aquarium, famed fishkeeper and author Dick Mills established a different stocking rule. Later on, most experienced fishkeepers adopted this regulation as their go-to guideline.

They claim we must consider the aquarium’s surface and floor space while calculating the stocking number. This is because oxygenation happens at the top, while bacteria degrade fish faeces at the bottom.

So, to properly apply this rule, we need to find the tank’s surface area first. To do that, multiply the tank’s length by its width. In our case, a 20-gallon long tank would be 30 inches long and 12 inches wide.

This gives us a surface area of 288 square inches (30×12). To calculate the total inches of fish the tank can hold, divide the surface area by 12 (surface area / 12).

To calculate how many fish your tank can hold, divide the answer from the previous by the height of your fish. ( the total inches of fish the tank can hold/fish’s height).

Let’s calculate the stocking numbers for a 20-gallon high tank and a 20-gallon long tank, both of which have dimensions of 24″ x 12″ x 16″.

Then take a conservative approach and assume the neon tetras are 1 inch tall. However, according to what I’ve read, their average height is 9-12 mm (0.35-0.47) inches in length.

Now, calculate the inches of tetras your neon tetra 20-gallon tank can support with the following formula:

Surface area / 12 = in inches of fish your tank can hold. This would be (24×12)/12= 24 inches of fish your tank can hold.

Finally, let’s calculate the total number of neon tetras a 20-gallon high tank can hold.

To do so, we’ll take the total inches that the tank can hold and divide it by their average height. In this case: 24/1 = 24 neon tetras

Let’s work out the surface area of a 20 gallon long tank. The dimensions of a 20-gallon long tank are: 30”L x 12”W x 12”H). Surface area = L x W = 30”x12” = 360. So a 20-gallon long tank can hold approximately 30 inches.

Thus, a 20-gallon long tank can hold (30)/1 = 30 neon tetras. So, a 20-gallon high tank can hold 24 neon tetras, and a 20-gallon long tank can hold 30 neon tetras.

Phew! That was a lot of math. But now you know two ways to figure out how many neon tetras can go into your 20-gallon tank.

However, I must mention that these stocking rules are very general and might not work for every fish keeper. They are meant to be a starting point for your stocking journey and not an end-all-be-all solution.

Furthermore, the answer differs based on how often you’re willing to do water changes, the decorations, the plants in your tank, and your fishkeeping experience.

How Many Neon Tetras Can I House in a 20-Gallon Tank with Betta?

how many neon tetras in a 20 gallon tank

Typically, bettas need at least a 2.5-gallon tank for themselves. However, most experts recommend keeping bettas in tanks of ideal minimum tank size of 5-gallon or 10-gallon.

So, if we assume the betta needs 5 gallons, you would have 15 gallons for neon tetras. If we apply the rule of ‘one inch per gallon,’ you could fit around 8.57 (15/1.75) neon tetras in that space- which rounds off to 9 total neons.

Thus, you could theoretically have 9 neon tetras and 1 betta in a 20-gallon tank. If you have two bettas, the maximum number of neon tetras would be 6.

How Many Neon Tetras and Guppies Can Live Together in a 20 Gallons Tank?

Male guppies grow up to 1.5 inches (1 inch on average), while females are typically larger than males, growing 2.4 inches (2 inches on average).

If we estimate the fish’s average length to be 2 inches, this gives us some wiggle room for error. So if you have 10 gallons of water for guppies, you can put 5 of them (10/2) in a 20-gallon tank.

Now you should have 10 gallons left over for the neon tetras. This calculates to 5.7 (10/1.75), which we will round up to 6 fish total.’

As a result, you can house 5 guppies and 6 neon tetras in a 20-gallon tank if you give each of these perfect tank mates 10 gallons of space.

What Happens If I Overstock My 20-Gallon Neon Tetra Tank?

Let me ask you something- have you ever been in a room so packed with people that you couldn’t breathe? Or felt like you were going to pass out from the heat?

If you have, then you know what it feels like to be an overstocked fish. Overcrowding is one of the leading causes of death in pet fish.

When a tank is overstocked, the water quality deteriorates rapidly. Ammonia and nitrite level spike, and oxygen levels drop. This aquarium ammonia poisoning creates foamy water, which makes it hard for the fish to breathe.

The foamy water also interferes with the fish’s fantastic sight because it pollutes the aquarium water. 

Overstocking the fish may also result in poor water conditions due to high fish waste. This may result in fluctuations in water conditions which can be rectified by ensuring frequent replacement water. 

As for the nitrogen cycle, overstocking can stall or completely halt the process. This is because beneficial bacteria need oxygen to convert ammonia and nitrite into nitrate. So these helpful bacteria will die.

Plus, overstocked tanks are more difficult to maintain because the filtration system has to work overtime to keep up with the waste produced by the fish. This puts a strain on the filter and can cause it to break down.

Thus, overstocking is a lose-lose situation for the fish and the fish keeper. So, be sure to stock your tank wisely!


Can Neon Tetras Eat Dead Fish?

Yes, neon tetras can consume deceased fish. It’s just like ordinary food to them, and if they are hungry, they will consume them.

Is It Possible For Neon Tetras To Die Quickly?

Neon tetras can live up to ten years if you keep their tank clean and properly cycled.

Do Neon Tetras Require Light at Nighttime?

Neon tetras do not require light at night but benefit from a dim light that simulates moonlight. This helps them feel maintain their circadian rhythm.

How Many Neon Tetras Can Survive in a 3-Gallon Tank?

You can place up to four to five small neon tetras in a 3-gallon tank. However, you can increase this number to seven or eight if you want more frequent water changes.

What Fish Should I Put in My 20-Gallon Fish Tank With Neon Tetras?

These are the ideal tank mates with neon tetras include:

How Many Neon Tetras In a 29-Gallon Tank?

Assuming the tetra’s mean height is 1.75 inches, you could add 16-17 tetras in a 29-gallon tank if you used the “1 inch per gallon” guideline. According to Dick Mill, 30 neon tetras can live in a 29-gallon tank.

How Many Neon Tetras in a 12-Gallon Tank?

A 12-gallon tank for neon tetras can accommodate six to seven neon tetras if you use the “1 inch per gallon” guideline.

How Many Neon Tetras in a 40-Gallon Tank?

If you use the “1 inch per gallon” guideline, you can accommodate 20 to 22 neon tetras in a 40-gallon tank.

How Many Neon Tetras Can I Put in a 30-Gallon Tank?

Using the “1 inch per gallon” guideline, you could place 15 to 16 neon tetras in a 30-gallon tank.

How Many Neon Tetras in a 55-Gallon Tank?

If you use the “1 inch per gallon” guideline, you could comfortably place 44 neon tetras in a 55-gallon tank.

How Many Neon Tetras in a 75-Gallon Tank?

A 75-gallon tank can accommodate 37 to 38 neon tetras if you use the “1-inch per gallon” rule of thumb.

How Many Neon Tetras in a 90-Gallon Tank?

By using the “1-inch per gallon” guideline, you could place 45 to 46 neon tetras in a 90-gallon tank.

Last Words

I know stocking a fish tank can be confusing, but I hope this article has helped clear some things up for you. Remember, when in doubt, it’s always best to err on the side of caution and go with a smaller number of fish.

As always, thanks for reading! Do you have any questions about stocking a 20-gallon tank with neon tetras? Let me know in the comments below!

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