Why Are My Guppies Staying in the Tank Corner?

It’s nice watching your fish swim around and interact with you and with each other. Seeing a bunch of colorful little guppies moving through the water is an aesthetic experience in itself. But what if your fish aren’t doing normal fish things like swimming, playing, and eating?

Sometimes, your guppies might gather into one corner of the tank and they’ll just stay there. Now what? Well, there are multiple possible causes for this behavior. Depending on the root of the issue, solutions will vary. In this article, we’ll discuss about these causes and solutions in great detail.

From inadequate temperature to ammonia poisoning, to stress, to birthing, I’ve included an exhaustive list of reasons why your guppies might be staying in the corner of the tank. Some cases require immediate attention, while others are harmless. If you’re curious why your fish are acting weird and hiding in the corner, make sure to give this article a thorough reading.

Your Guppy Fish Might Be Stressed

Stress is usually the main cause of unusual behaviors such as hiding and lack of physical activity in guppies. There might be many different causes of stress, including serious ones that require immediate attention. Such causes include suboptimal water parameters, unsanitary conditions, sickness, fluctuations of water temperature, unsuitable water temperatures, and living in a crowded aquarium.

Other less severe but still important causes include a sudden change of environment, violence from other fish in the tank, and lack of hiding spots such as plants and other decorations. As you can see, guppies can feel stress due to a variety of physical and psychological triggers. But let’s take these causes one by one to learn more about them.

The Water Temperature Is Off

Water is a huge part of a guppy’s environment. Any sudden change in water parameters can cause stress in your fish. Besides sudden fluctuations, suboptimal water parameters are also a significant source of stress. Water that’s too warm or too cold negatively impacts your guppies’ health. Water that’s too warm for guppies, such as anything above 86 °F (30 °C), leads to a fall in oxygen levels.

When oxygen levels fall, your guppies might be gathering into a corner and coming up to the surface to gasp for air. When the water is too cold, your guppies’ metabolism slows down dramatically, and your fish might start sleeping for longer. Either way, when the water temperature is off, your fish won’t be as active.

In the wild, guppies live in tropical areas with water temperatures ranging between 65-85 °F (18-30 °C). In captivity, it’s best to stick to a narrower range around 75-78 °F (24-26 °C) to avoid sudden fluctuations in temperature. The best way to maintain and monitor the water temperature in your guppy tank is by using an aquarium heater and a thermometer.

New Guppies and Acclimation

If you’ve added new guppies to your tank and you notice they’re constantly hiding in the corner, don’t worry! This is normal, albeit not a good thing. As I’ve already mentioned, guppies get stressed when exposed to sudden fluctuations in water parameters. Adding a new guppy to your tank all of a sudden is usually a rough experience for the fish. That’s why acclimation is important!

If your new fish receives proper acclimation, you can easily prevent this from happening. The key is to introduce your fish to the new water slowly. It’s best to first put your new fish in a separate tank before they get used to the new water parameters and environment. If you can’t do that, you can still introduce your new guppy into the main tank.

Here’s a good tip! If you’ve brought your new guppy home in a plastic bag, you can place the bag in the aquarium. Keep the bag in the aquarium for around 30 minutes. The water in the bag will warm up slowly until it reaches aquarium temperature levels. At that point, you can safely free your new guppies into the tank.

Your guppies might still be hiding for a while because they aren’t familiar with the new environment, but they shouldn’t experience any more physical stress after acclimation. As long as there’s no shock during transportation or acclimation, your new guppies will get used to the new tank relatively quickly.

New Tanks and Ammonia Accumulation

A common problem for many new pet fish owners is the tank setup. A new tank takes time to prepare. Even if you install a biological filter, you need some time to cycle your new aquarium. It usually takes 1-3 weeks for the full biological maturation of an aquarium. If you add your fish in too quickly, waste by-products will soon accumulate.

If you haven’t properly prepared your tank, the filter won’t work to full parameters. As a result, harmful bacteria and waste products won’t be broken down effectively. As ammonia levels rise in the water, your fish can suffer ammonia burns, swimming issues, and even sudden death. Your fish might be hiding in the corner due to ammonia-induced sickness.

This is a problem that requires immediate attention because even low levels of ammonia can be lethal for your guppy fish. Make sure you cycle your tank for at least one week, and preferably up to three weeks before introducing your new fish. Use a biological filter to prevent ammonia spikes. Adding live plants and even using nitrifying bacteria can also help speed up the biological maturation process.

Unsanitary Tank Conditions

Besides just ammonia, several other harmful things are lurking in unclean water. If your fish suddenly start staying in the corner of the tank, you might also be dealing with harmful levels of nitrites, nitrates, and harmful bacteria. The only effective way of removing nitrates from your water tank is through weekly water changes.

Another thing to remember is that harmful compounds don’t just stay in the water. Bacteria can especially stick to surfaces such as tank walls, decorations, and even in the substrate. Hygiene is as important as feeding, and a water filter won’t save you from having to clean your tank and change your water every once in a while.

It’s best if you can complete a large water change (30-50% of water volume) at least once weekly. Besides that, you’ll also want to monitor the levels of chlorine and heavy metals in your water. A good water conditioner can help you keep these levels in check.

Your Guppies Might Be Sick

Besides ammonia poisoning or suboptimal water parameters, guppies can also hide in the corner of the tank for other reasons. These tiny fish are susceptible to viruses and bacterial infections. Typically, when guppies come into contact with bad bacteria, when they develop diseases such as fin and rot or dropsy (swollen belly), they’ll start hiding. You may not notice your fish being sick until the infection takes its toll.

Keep an eye on your guppies. If you notice any fish that starts hiding, try inspecting it up-close. Prevention is better than management, but if you catch the disease early on, treatment will be easier and more likely to succeed. Because most fish diseases are caused by bad bacteria, the best way to prevent infection in your fish is to maintain a clean aquarium.

Depending on the cause of the sickness, different treatments can be useful. Water replacement is the first thing to do when you notice sickness in your fish. It’s even better if you can quarantine your sick fish in a different tank. There’s also a variety of antibiotics and anti-fungal medicines to choose from. But it’s best to consult a specialist as soon as you notice anything wrong with your fish.

Your Guppies Might Be Bullied

Nobody likes being bullied, but I imagine it’s even less cool when you don’t have arms or legs to protect yourself. I guess flippers don’t make good weapons. To make things worse, guppies are tiny fish so many other species can outsize them. This wouldn’t be a problem in most cases, as guppies are friendly, sociable, and peaceful fish.

They get along with a variety of other fish and they aren’t prone to violence. The issues start when guppies have to share a tank with aggressive fish, especially if these are larger than them. Tiger barbs, cichlids, and angelfish are all a no-no for a guppy tank. Avoid larger, territorial fish. They will often bite, chase, and even eat your guppies.

The prospect of being eaten alive sounds stressful, alright. I’d probably feel the same if I were to be closed in a cage with a pride of lions. And if you have no plants or hiding spots in your aquarium, it’s easy to see why your defenseless, scared guppies tend to flock together in the corner.

Female Guppies Giving Birth

Saving the good news for last. Sometimes, when female guppies start hiding near the bottom or in the corner of the tank, there’s nothing to be worried about! If one of your female guppies starts acting like this, it means she’s preparing to give birth.

Be ready to move your birthing female guppy to a different tank. If you want to save your guppies from being eaten, it’s best to keep them away from the main tank before they reach a certain size. But I always advise moving the female guppy in a different tank while she’s giving birth.

When she’s done, gently transfer her back into the main tank. Don’t let her give birth in the main tank. It’s way riskier to move the baby guppies after birth because they’re too small and fragile and they get hurt easily.


Fish might not communicate in the same way as other animals, but their behavior can tell us all we need to know about their needs and wellbeing. When your guppies are acting strange and hiding or keeping static for a long period of time, it’s safe to assume that something’s wrong.

Sickness, water temperature, accumulation of waste by-products, and even conflict with other fish can stress out your guppies and cause lots of problems. So, always keep an eye out for your fish. If they start hiding or gathering in the corner of the tank, something might be going on that needs your attention.

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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