How Many Guppies in 10 Gallon Fish Tank?


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Are you a beginner and want to start your first fish tank with some guppies? Do you want to know how many guppies you can fit in a 10-gallon aquarium? In this article, I will tell you how to calculate the number of guppies you can place in a fish tank.

Before I go into details on how to determine the number of guppy fish per gallon, here is my recommendation for a 10 gallon aquarium:

I recommend adding 5-10 adult guppies to a 10 gallon fish tank, depending on your setup, filtration, substrate and frequency of water changes.

How to Calculate the Number of Guppies for a Fish Tank?

I use the 1 inch of fish per 1 gallon of water rule to determine the maximum number of guppies per aquarium.

If you have a 10 gallon aquarium, the water volume will not be 10 gallon. The gravel, the internal or sponge filter, the decoration or live plants, the heater will take up space. So technically you can’t add 10 gallons of water in a 10 gallon fish tank.

That said, your tank will hold around 7-8 gallons of water.

An adult guppy can reach up to 1.5 inches (3.8 cm), without counting their tail fins.

So in 10 gallons of water you could place roughly 7 adult guppies (10 gallon / 1.5 inches = 6.66).

I would not recommend adding more than 10 guppies in a 10 gallons aquarium, if you are just starting out.

Start with less fish, and establish your aquarium first. This way you can learn how to care for your guppy fish.

Here is a crazy video of hundreds of guppies in a small tank:

You should avoid such aquarium setup!

Is it Possible to Add More Guppies to 10 Gallons Aquarium?

If you are like me, and love overcrowded fish tanks, you are probably wondering how to get around the general rule of thumb: 1 inch of fish per gallon of water.

There are few things you can do:

  • Get a better internal filter or maybe an external filter
  • Add good bio filter media to your filter (I use Seachem Matrix and Ehiem Substrat Pro from Amazon)
  • Add live plants to your tank (add fast-growing plants)
  • Use special substrate (not gravel)
  • Reduce feeding to minimal (once every other day)
  • Do weekly water changes (30-50%)

Now, I will explain each on in particular.

Use Internal or External Filter

Most aquarium kits come with an internal filter. These filters are sized perfectly for a 10 gallons aquarium but are not meant to run an overstocked aquarium.

To increase the fish capacity of your aquarium, you can buy a bigger internal filter, which has better performance, a higher flow rate, etc.

It would be even better to buy an external canister filter or a hang-on-back filter. This way you can increase the water volume in your fish tank because the filter will not take up space.

On top of that, the external filter holds a certain amount of water, so you can increase the water volume this way.

Get a filter, which is oversized. For a 10 gallon aquarium, I recommend the Aqueon QuiteFlow 20 HOB filter, which is a hang-on-back filter. This filter is recommended for 20 gallons. It has a flow rate of 125 GPH (470L/hr), so it will work fine in your overstock 10 gallon fish tank.

If your tank has a lid, which can’t be removed or replaced, you might consider an external canister filter. For a 10 gallon, over-stocked guppy aquarium I recommend the SunSun HW-603B filter. This is a very quiet and efficient external canister filter. It consumes only 6W and has a flow rate of 100 GPH (400L/hr).

Use Good Filter Media

The performance of the filter is only one thing. You also need to add good filter media. In an overstocked aquarium sponge filter media will not cut it. You need the real stuff.

Along with the usual sponge filter, you need biological filter media as well. The sponge filter will catch the heavy muck, while the biological filter media will provide extreme surface area for the beneficial bacteria to decompose the harmful toxins such as ammonia and nitrite.

In all of my tanks I use the Seachem Matrix and the Eheim Substrat Pro biological filter media. With these two filter media I had great success over the years. I highly recommend them.

Sure, you can use other, cheaper filter media, just be sure that those offer enough surface area for the bacteria.

Use Live Plants

I love planted tanks. I have live plants in all my aquariums. Besides the fact that live plants are very pleasing to the eyes, they can also help a lot in improving the quality of the water.

Yes, live plants will consume the toxins produced by the fish waste and will use it to grow. Fast-growing plants will extract more nutrients from the water column. I recommend using one or more of the following plants in your guppy fish tank:

  • Guppy grass
  • Java ferns
  • Hornworts
  • Watersprite
  • Wisteria
  • Amazon sword
  • American waterweed (Elodea)

You can also add flowing plants such as:

  • Duckweed
  • Amazon frogbit
  • Giant duckweed
  • Water lettuce

Plants will also help in reducing or eliminating algae growth in your guppy aquarium.

Please remember, that plants need light. If you add plants to your tank, make sure that the lights are on at least 6-8 hours a day. In absence of light, your plants will slowly die off and will pollute the water.

Time-to-time you might also want to help your plants with some nutrients. So you can add aquarium plant fertilizer to your tank. This is not a must, but it helps to keep your plants healthy.

Use Special Substrate

Gravel is the most commonly used substrate in aquariums. It is cheap, looks good and it is easy to clean. However, it only takes up space and do not help your aquarium in the process of self-cleaning.

There are various substrates that you can use to replace gravel. Some of these substrates such as the Seachem Flourite will help develop more nitrifying bacteria, which will break down fish waste.

If you don’t want to invest in a special substrate, please vacuum the gravel every time you do a water change. You can use an aquarium gravel vacuum for this purpose.

Reduce Fish Feeding

Guppies are always hungry. They can eat all day long. Overfeeding is one of the main problems when it comes to fish diseases and bad water quality.

Adult guppies don’t need much food. Feeding them every other day will keep them healthy and will not result in huge water pollution.

When feeding, add only a small pinch of food at once. Wait until the fish eat all the food you gave them. Repeat the process until you think your fish eat enough.

Perform Regular Tank Maintenance & Water Changes

An overstocked tank needs more attention and care. While the waste will accumulate much faster, you will need to do water changes more often.

If you have a good filter and good filter media, you will be fine with one weekly water change. I recommend doing 30-50% weekly water changes on your overstocked guppy aquarium, in order to avoid any disaster.

Also clean your filter regularly. You should wash the filter media in aquarium water every other week. Don’t use tap water to wash your filter media, because chlorine will kill all your beneficial bacteria. Also don’t keep the biological media dry for too long, because that will also kill off the good bacteria.

Wrapping Up

I really hope, that my guide has helped you not only in figuring out how many guppies you can place in a 10-gallon aquarium, but also on how to make your fish tank better.

If you have any questions regarding guppies, feel free to leave a comment or submit an email via the contact form.

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Updated: October 26, 2021
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