How Many Guppies to Keep in a 55-Gallon Tank?

If you’ve prepared yourself to become a proud guppy owner, the first thing to get out of the way is the tank. A 55-gallon tank is a decent option if you want to build a sustainable and diverse aquarium fauna.

The general advice would be to have one guppy per gallon of water. This means that a 10-gallon tank is a fit option for around 5 guppies. A 55 one will take up to 27 guppies. These are, however, approximations since there are more factors at play here than the number of guppies.

These include each guppy’s size, gender distribution, and overall tank dynamics and setup.

Today, we will discuss guppy distribution in a 55-gallon tank to see what you should consider when preparing the setup.

How to Set Up a 55-Gallon Tank for Guppies?

As a guppy keeper, you have two overarching goals: build a vivid and balanced aquatic environment and provide guppies with comfort and a healthy and balanced lifestyle. The first thing to consider is the guppy-to-tank-size ratio.

Here are some points to keep in mind when setting up the tank:

  • 55 gallons isn’t actually 55 gallons – This is pure physics. A 55-gallon tank won’t hold 55 gallons of water; it will be 50 at most. The rest will be filled with fish, underwater decoration, rocks, plants, substrate, etc. All these will push the water level, forcing you to reconsider the water volume necessary. So, you can’t calculate the number of guppies according to the tank’s size, but the water volume it will realistically hold. I would advise keeping between 20 to 25 guppies at most in a 55-gallon tank due to this reason alone.
  • Control the male-to-female ratio – Male-female dynamics can reach explosive proportions during the mating phase, as males can be quite pushy and persistent. This can eventually stress out the female, lowering its immune system and leaving it vulnerable to infections. You can solve this problem by controlling the number of males. I recommend having at most 1 male for every 3 females, reducing male-to-female interactions, and allowing guppy females some breathing room.
  • Consider the tank decorations beforehand – The more decorations you have and the more massive they are, the more the water level will increase. It’s important to maintain adequate water volume and find a balance between the water’s level and the aquatic decorations. Your guppies need a lot of water volume, as well as plants, rocks, caves, etc.
  • Assess the tank dynamics – Sometimes, your guppies may appear uncomfortable in their new tank despite all your efforts. Even with enough room, some males may be more aggressive and territorial, leading to constant confrontation. In this case, it’s imperative to remove the aggressive fish and rebalance your guppy population. This will prevent guppy stress which often relates to a lower immune system and predisposition to infections, parasites, and illness.

Can You Keep More Guppies in Your Fish Tank?

Yes, you can, but only after taking some necessary precautions. Most guppy keepers will do whatever possible to crowd as many guppies in one tank as they can. More guppies equal a more exhilarating and diverse aquarium, but it will also lead to various problems along the way.

In theory, you can cram several guppies above the recommended limit, so long as you follow some guidelines.

Here’s what to do to ensure a healthy and stable guppy population even with more specimens than intended:

– Have a Powerful Filtration System in Place

Simply put, the filter will act as your tank’s kidney, cleansing the water and providing your guppies with a safe and healthy environment. The problem is that the bigger and more crowded the tank, the larger and more powerful the filter should be.

It’s important here to find the ideal balance between the filtration system’s power, the available water volume, and the number of guppies. A weak filtration system will fail to deliver the expected results, while one that’s too powerful can hurt the fish.

Set up a filtration system that meets your tank’s demands without going overboard.

The filtration system should protect guppies against harmful bacteria as well as chemicals like nitrates and ammonia. Ammonia, in particular, is deadly for your guppies, and it is common in overcrowded tanks. Ammonia build-up is the direct result of unconsumed food decaying in the tank and the accumulation of fish waste over time.

In time, you will begin to notice ammonia poisoning symptoms in your guppies, a condition that’s deadly when left untreated.

You can easily prevent this problem by monitoring the ammonia levels and ensuring optimal filtration.

– Have a Rich Aquatic Biome

Every tank should have its fair share of live plants. These serve multiple purposes, including functioning as hiding spots, food for fish, or producing oxygen, and cleaning the water of harmful toxins.

Live plants are extremely important in a tank predisposed to ammonia build-up due to a higher number of fish. A diversity of plants will offer your fish something to nibble and cleanse the water of nitrates and ammonia.

They can also serve as shelter for guppy fry, protecting them against the adults or other fish species that may hunt them down.

– Understand the Importance of Aeration

Aeration is the process of allowing more oxygen to enrich the tank water. You can achieve this by exposing the water tank to fresh air, especially if you have a lid on to prevent guppies from jumping out.

Aeration is necessary even for tanks with plenty of live plants. Basically, you need as many tools as you can get when your tank is overburdened with more guppies than recommended. Relying on the plants alone to provide optimal oxygenation won’t cut it.

– Regular Tank Maintenance

This is one of the most important aspects to consider. Regular tank maintenance will prevent a variety of problems along the way, including ammonia build-up and nitrates formation. Your guppies will invariably make a lot of mess. Having more guppies than the recommended number will exacerbate that problem.

I advise cleaning the tank regularly to prevent fish waste accumulation and food decaying on the substrate. With more fish in the tank, you will also need to check for dead or dying guppies constantly. Having a lot of fish, plants, and aquatic decorations can make it difficult to spot dead fish.

Leaving them in the tank will poison the water as they will start decaying. This will lead to ammonia build-up, poisoning the other fish. Such an event can decimate your entire guppy population in a matter of days.

– Control the Breeding

The more guppies you have, the higher the chance that they will breed, leading to a flood of guppy fry. A guppy female will generally deliver around 20-50 fry every 30 days. In some cases, however, the female can produce in excess of 100 fry, or even more than 200. Now expand those numbers by how many females you have, and you will see the problem.

While most fry will fall prey to adult fish, who will hunt them down immediately, a small number will survive and adapt. This can lead to tank overcrowding fast.

I suggest monitoring the guppy population, identifying the pregnant females, and removing them before the delivery. You can identify them by the inflated belly and the dark pregnant spot in the lower abdomen.


Despite all the solutions I’ve provided, I still recommend you to stick to the golden rule of 1 guppy per 2 gallons of water. This will provide your guppies with all the room they need while keeping the water clean and fresh for longer.

Overcrowding can cause a variety of problems, no matter how careful you are and how many precautions you take. Stay on the safe side and keep 20 to 25 guppies at most in a 55-gallon tank.

avatar Noah
I’m Noah, chief editor at VIVO Pets and the proud owner of a playful, energetic husky (Max). I’ve been a volunteer at Rex Animal Rescue for over 2 years. I love learning and writing about different animals that can be kept as pets. read more...

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