Quite frequently, I catch worrying behaviors in my tank. For example, there were periods when I saw my zebra danio staying at the bottom of the tank without moving. As I gained more experience, I learned what causes the issue and how to deal with it. Now, I am willing to share what I’ve learned.
Danios typically stay at the bottom of the tank when stressed, secondary to aggressive tankmates and inappropriate water conditions, including elevated ammonia, nitrates, and nitrites. However, danios may also swim at the bottom due to a swim bladder disease, which compromises the fish’s buoyancy.
As we move forward, I will share four essential steps that might help you with danios that refuse to leave the lower sections. I will also explain in which cases you have nothing to worry about, or on the other hand, have nothing to do to solve the issue.
Why is my Danio Staying at the Bottom?
Zebra danios are small fish that spend most of their time in the upper sections of the tank. For that reason, any danio that is always hanging out at the bottom should concern you. Some factors that may encourage such behavior include:
1. Some Danios Enjoy the Bottom
Don’t be so quick to interpret such behavior as a sign of trouble. Yes, zebra danios have a reputation for spending most of their time in the aquarium’s upper sections, and any danio that frequents the bottom deserves some attention.
However, you should only react with concern if the danio in question has also manifested additional signs such as rapid breathing, inflammation of the gills, and listlessness, to mention but a few.
If your zebra danio is entirely healthy, then you have to consider the possibility that it actually likes swimming at the bottom of the tank. Zebra danios don’t have to stay at the top. Some of them prefer to occupy other sections.
2. The Danio is Sleeping
Most animals sleep. They have a period of the day or night during which their bodies shut down to rejuvenate. Fish are no different. In fact, researchers have found that Zebra Danios sleep just like humans. The lack of eyelids means that they cannot close their eyes.
However, they can become motionless, especially at night, when the lights are off. Sleeping fish will awaken when you turn the lights back on. They will also respond to stimuli. You can try gently nudging a fish that is lying at the bottom of the tank.
If it comes to life and proceeds to swim away from the bottom, you can assume that it was just sleeping. If a fish refuses to abandon its position at the bottom of the tank, even in the presence of food, then you can conclude that sleep isn’t the cause of the creature’s behavior.
3. There are Too Few Danios in the Tank
Zebra danios are shoaling fish, so they need the company of other zebra danios. If you keep them in small groups, the stress could encourage them to frequent the bottom. That is because they lack the confidence to swim in the open.
Zebra danios that are living in small groups may also bully one another. A group of 3 is particularly problematic because two danios may gang up on the third. The hostility may encourage the danio in question to seek refuge at the bottom of the tank.
4. They Share the Tank With Aggressive Tankmates
Even though zebra danios are social fish, you can’t just pair them with any random species. The wrong fish will make your danios miserable. Predatory creatures like Redtail Catfish will discourage the danios from swimming out in the open. As a result, they will frequent the bottom, where they are less likely to encounter trouble.
5. The Tank is not Suitable for Danios
Have you tested the water? Sometimes, zebra danios escape to the bottom because the parameters in the tank are wrong. If the aquarium doesn’t have a heater, the temperature will keep fluctuating.
In case the filter isn’t working correctly, the water will be filled with rotting leftovers and various pollutants. A poorly maintained tank encourages ammonia levels to spike. Ammonia poisoning is no joke.
It will affect your fish’s ability to breathe and make them vulnerable to diseases. The same is true for toxins like nitrates and chlorine. If you have some confidence in the parameters of your tank, you should investigate the size.
Yes, zebra danios prefer to live in large groups. However, those large groups will become a source of distress if the tank is too small. These fish are active and need room to explore. If your tank is crowded, some of them will look for solace at the bottom of the tank.
6. The Danio is Carrying a Disease
Like humans, the presence of parasites and bacterial infections can exhaust your zebra danios. This is why ailments like the flukes have lethargy as a symptom. Sick fish don’t move as much because they don’t have the strength.
If their illnesses persist, they will sit at the bottom because they are so drained. You may also see that the danios are breathing heavily and that their colors have faded. Lethargic fish may die if their illnesses are not treated.
7. The Danio Caught a Swim Bladder Disease
The swim bladder is an organ that fish use to maintain their balance and buoyancy. If an illness or injury compromises the organ, your danio’s ability to swim will suffer. Some danios stay at the bottom because they don’t have a choice.
Because their swim bladder functions have been compromised, they can’t swim up and away from the bottom. And whenever they do, they hover for a moment before sinking back down.
8. Your Danios is Relatively Old
Some zebra danios are old, and lethargy is a sign of old age in some fish. Older fish are not as active as their younger counterparts. Some of them spend most of their time at the bottom because they don’t have the strength to swim.
Others are still strong enough to swim in the tank’s upper sections, but they have to rest at the bottom every once in a while. The average lifespan of danios is 3.5 years. If your danio is approaching this age, you may conclude that it has become old.
9. The Fish is Stressed
It is quite common for stressed fish to frequent the bottom, especially if their tank doesn’t have hiding places. Stress has various causes, including parasites, aggressive tankmates, fluctuating temperatures, low parameters, overcrowding, and temperature shock, to mention but a few.
Zebra danios new to an aquarium may stay at the bottom because they are not accustomed to their new environment. In this particular case, the behavior is probably temporary and will resolve as time passes.
How to Treat Zebra Danios that Always Stay at the Bottom?
If your zebra danio is old, you cannot treat it. As was mentioned, these creatures have an average lifespan of three and a half years. But if the danio is relatively young, you can use the following to reverse its behavior:
1. Making the Water Suitable for Danios
Start with a 50 percent water change; you can’t go wrong with it. It will eliminate ammonia and lower nitrates and nitrites. You should also remove all the pollutants you can see in the water, including vacuuming the substrate.
It is also worth considering conditioners like Seachem Prime (link to Amazon), that removes toxins like chlorine and chloramine. They will also neutralize ammonia, making your tank safer. I’ve been using that product for years with great success.
If you are not sure what your tank’s situation is, I highly recommend getting the API Aquarium Test Kit (link to Amazon). That particular bundle will measure your pH, nitrates, nitrites, and ammonia. Within 5 minutes, you’ll know if something has gone wrong.
That kit also lasts for extended periods and therefore worth the investment. When it comes to water parameters, it will help if you maintain the right temperature and pH for danios, which are 64 to 77 degrees F and 6-8, respectively.
If your device doesn’t work correctly and the temperature fluctuates, I highly suggest checking my recommendation for an aquarium heater. After testing multiple heaters that failed, that is the only device that keeps my temperature stable enough for sensitive fish.
Zebra danios require functional heaters, filters, and pumps. This is the only way to prevent temperature fluctuations and oxygen deficiencies. The presence of a filter also prevents pollutants from accumulating in the tank.
2. Picking the Right Tankmates
When it comes to populating your zebra danio tank with fish, avoid species with long fins that the danios will nip. It would help if you also avoid fish that are either too aggressive or too docile. Aggressive fish will attack the danios, especially if they are more prominent.
On the other hand, zebra danios will distress species that are too docile. Stick with peaceful fish within the same size range as danios, such as honey gourami, harlequin rasbora, clown pleco, guppies, and small barbs.
3. Dealing With Swim Bladder Disease in Danios
If a congenital disability causes this ailment, it can’t be treated. An injured zebra danio can be quarantined and treated with salt baths. Though, in most cases, besides improving their diet, you can do little more than wait for the swim bladder to heal on its own.
This is on top of treating any injuries on the outside against bacterial and fungal infections. Some injuries to the swim bladder may refuse to heal. In other situations, the swim bladder may heal, but the fish won’t recover its ability to swim properly.
Zebra danios, whose swim bladder disease was caused by constipation, are less of a concern. A few days of fasting and a diet consisting of peeled and cooked peas will eliminate the blockage in their digestive system, allowing the swim bladder to recover.
4. Lowering Stress in Danio Fish
You can eliminate stress by keeping at least six danios in the tank. A smaller number will encourage bullying because danios do not feel as safe in small groups. If you have plenty of danios, but they are still anxious, give them plants and decorations that they can use as hiding places.
Zebra danios that are new to the tank shouldn’t concern you. They may swim at the bottom in the beginning. But once they grow accustomed to the tank, they will join the other fish in the tank’s upper sections.
You should also ensure that the tank is at least 10 gallons to prevent overcrowding. If the tank is too small, the danios will encounter their tankmates more frequently. That might stress the fish, forcing them to swim downwards.
Why is My Zebra Danio Hiding?
Zebra danios typically hide when they feel stressed, usually due to bullying tankmates. However, that also happens when the temperature and pH are not suitable. Some danios also go into hiding towards nighttime because it allows them to stay safe while sleeping and less aware of dangers.
As you can see, danios will hide for any number of reasons. These factors will force the fish to get behind heaters, rocks, plants, filters, etc. Some of them will change the fish’s swimming behavior, forcing it to swim at the bottom.
- Sleep – Danios know that sleep makes them vulnerable. For that reason, some of them prefer to stay out of sight when they sleep. This shouldn’t concern you.
- Stress – This is the most common cause of hiding in danio fish. The anxiety caused by extreme temperatures, dangerous ammonia levels, crowded tanks, and the like will encourage danios to stay out of sight.
- Bullies – This goes without saying. If your tank is filled with large and aggressive fish, your danios will spend most of their time hiding because they don’t feel secure.
- School – Zebra danios are shoaling fish that should be kept in groups of at least 6. Small groups make them feel less secure. An insecure fish will remain in hiding until the situation in its environment changes.
- Tank Conditions – Poor tank conditions cause stress in fish. That includes tanks with the wrong pH, temperature, and hardness. You can expect similar results in tanks that are too small. Because the zebra danios cannot escape the tank, they will respond by either laying at the bottom or going into hiding.
- New Tank – Danios new to a tank will hide because they are not accustomed to the aquarium. The unfamiliar environment makes them anxious, and they will stay hiding until they grow comfortable with their new situation.
- Disease – Sick zebra danios will go into hiding because the presence of an illness makes them vulnerable. They know that they are too weak to fight off predators. So they will remain in hiding until their condition improves.
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If your danio is staying at the bottom, the first step would be testing the water parameters. You can tell if the pH, nitrates, nitrites, and ammonia are not suitable for danios using a testing kit. Bear in mind that they require 64 to 77 degrees F and a pH of 6-8.
If the water is okay, check the danio’s tankmates. If you see that they harass their companions, separate the problematic fish. That will lower the stress and might get your danio out from its hiding spot.
In case everything seems okay besides the odd danio’s behavior, you may conclude that it’s merely the fish’s personality. Some danios prefer to stay at the bottom for no apparent reason.