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If you know much about how fish breathe inside water, it can be unsettling if you notice yours coming up to the surface, almost like they are looking to catch a breath outside the tank.
Well, it should be unsettling, though not in all situations.
See, fish take water into their mouth, pass it through the gills just behind the head on each side to absorb oxygen dissolved in the water and release carbon dioxide, which is then expelled into the tank.
Now, for oxygen to dissolve in the water, it needs to be in contact with the outside air. This happens more at the top of the tank near the surface than at the bottom.
As such, if you have a fish coming to the water surface, there might be more oxygen at the top than the bottom of the tank.
Your fish is only trying to survive with the limited oxygen supply in the tank.
This is more likely to happen in a deep tank than in long, shallow aquariums, especially if you do not have an air pump,
Please note this is not an ideal situation for any fish, and you should consider adding an air pump to your tank or increase your filter flow rate to improve aeration.
Fish Staying at The Top of Your Fish Tank
As I mentioned, the most likely reason for your fish staying at the top of the tank is poor aeration at the bottom.
However, there are a few more reasons why fish swim at the top of a tank.
First, if you own fish of the gourami family, such as betta, you will notice them come to the surface for air because they can.
They have a unique organ called the labyrinth that allows them to breath from the surface of the water.
The second possibility is your fish is (or are) a top dwelling species that naturally like to swim near the surface. You’ll also notice these finnies prefer to feed on floating food and will rarely swim to the bottom.
Betta fish, golden wonder and clown killifish, Furcata rainbow fish, common and orange danio, brown pencil fish, and silver hatchet fish are a few top dwelling fish you are likely to find in the hobby.
Some fish ailments and conditions, such as swim bladder disease, cause buoyancy issues in fish and is another reason for fish staying near the water surface.
Fish suffering from swim bladder disorder may sink to the bottom, float to the top, float up-side-down or on their side and struggle to maintain normal position.
Ammonia (poor water quality) is the fourth reason for fish hanging at the surface of the water.
Ammonia (and nitrites) produced by fish waste is lethal at any level above zero. In a fully cycled tank, ammonia would only accumulate due to a filter failure, poor aquarium maintenance, and overstocking.
If ammonia is causing your fish to swim near the top of your tank, you’ll need to remove and detoxify your water to prevent your finnies death.
Change 50 percent of your water and add ammonia removers to convert the toxic ammonia to ammonium.
Sadly, one last reason your fish could be floating at the top of your tank is death. Essentially, a dead fish will look lifeless with no visible movement around the gills, abdomen, and fins.
Side note, it’s not all fish that float when they die. In fact, most will sink and only come up when they decomposing and become lighter than the tank water.
Only fish with gases trapped in their body cavities (for instance, those that die from some bacterial infections) will float immediately after death.
Below is a quick scan list of reasons that may cause your fish to swim near the top of the tank (near the water surface).
- Poor aeration (low oxygen) inside your tank
- Bacterial and parasitic infection that cause gas to be trapped inside the fish, resulting in incresed bouyancy.
- Swim bladder disease
- Ammonia, nitrates, and poor water conditions
- Top dwelling fish
- Labyrinth fish like gouramis that can breath surface air
Fish at The Surface After Doing A Water Change
The few times I’ve been in this situation, my fish will swim to the top of the tank, near the surface, and gasp for air after a water change.
Perhaps it’s what you are experiencing as well.
Well, there are several reasons this happens. But most times, it has something to do with the water you added to your fish tank.
If the water quality is compromised thus not safe for use in a fish tank, your fish will react by gasping, swimming to the top, swimming restlessly, and looking lethargic.
You especially don’t want water with chemicals, more so ammonia, in your fish tank. Chlorine and metals like iron and copper can also affect your fish.
In the case of metals like copper, your snails and shrimp will perhaps show signs of stress and succumb before your fish. It’s not a good way to know there is a problem, but it will help save your fish.
Below are common elements you are likely to find in tap (or well) water that will cause your fish to swim and gasp at the top of the tank (near the surface).
Some I’ve mentioned in the intro above.
- Chlorine (or Chloramine): Many municipalities add chlorine or chloramine to their water. The chemicals are meant to remove contaminants and make the water safe for human consumption but are detrimental to fish gills. Chlorine often affects a fish breathing, hence the gasping at the top of the tank.
- Iron: Iron is more likely to be present in tap water, especially in old age-old pipeworks made from galvanized iron (G.I). Although usually not found in high concentrations enough to harm your fish, it can energize algae growth.
- Copper: Same with iron, copper is only found in traces in tap water, possibly from copper plumbing. Fortunately, most tropical finnies can withstand a small amount of copper, but inverts can’t and will succumb rather readily.
- Phosphates (and sometimes Silicates): This element is not common in tap water, but you’ll get traces in well or bore water. Phosphates (and Silicates) won’t affect your fish and are unlikely to make them gasp at the top of the tank, but they will cause exponential algae growth.
- Ammonia: Ammonia and nitrites may be present in water, but it is usually a result of fish waste in an existing fish tank. So, if ammonia is the reason your fish are gasping, chances are your water changes are too small to expel the toxins in your aquarium.
Now that we’ve seen some of the scenarios you may be dealing with, let’s discuss the solutions.
Essentially, the first thing you want to do before any water change is to condition your tap water to make it safe for your fish. This is assuming you’ve already done a water test and determined the chemical composition of the water.
If you are yet to do the water test, I recommend you get to it as soon as you possibly can. The analysis will help you make informed decisions about what you need to do to maintain healthy conditions in your aquarium.
Use Seachem prime water conditoner to remove chlorine and chloromine from tap or well water before adding it to your tank.
This conditioner will also remove ammonia, nitrites, and some heavy metals found in tap water.
You can also use absorbents for a specific element, more so when you have a lot of one chemical or heavy metal in your water. For instance, Phosguard will remove phosphates and silicates and cuprisorb will absorb copper.
Thats said, an easy wholesome solution to use would be to use reverse osmosis (R.O.) water to refill your fish tank. But you would need to remineralize it, especially when adding to a freshwater (tropical) fish tank.
Tropical fish need some level of water hardness to thrive, with some like cichlids needed hard water than, say, tetras or cory cats.
Fish Swimming at The Top of The Tank at Night
Several types of fish, such as clownfish, sleep at the top of the tank. They will typically come up whenever they need to take a rest and most likely sleep on one spot every day.
Some finnies also come up to the top of the tank at night to spawn.
However, I haven’t seen this behavior with many freshwater aquarium fish. It’s exhibited more by marine finnies such as clownfish, mandarin, and yellow goby.
Thats all for this post.
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Happy fish keeping🐠🐟.