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6 Reasons Your Betta Fish Is Lethargic After A Water Change!

With betta fish being the second best selling fish species in the world right now, we constantly see people reaching out with a wide range of different questions about what people should be doing to keep their pet betta fish as healthy and happy as possible.

We have a large number of articles on our blog about caring for a betta fish already but more recently, there have been a number of people reaching out to specifically ask for advice on why their pet betta fish is lethargic after a water change in its tank.

This seems to be a very common problem, especially amongst people who are new to the fish keeping hobby so we wanted to publish our own article on the topic.

Please note that in addition to your betta fish being lethargic, betta pineconing and clamped fins can also be common after a water change but our article should be able to help you deal with the problem and get your betta back to normal quickly.

Why Your Betta Fish Is Lethargic After A Water Change!

The majority of betta fish that are lethargic after a water change will usually be having problems with either the chlorine levels in their tank or the water temperature due to new water in their tank.

Those are both very common problems that we see on a regular basis but our list below includes some of the less common issues then we will take a look at each of them in more detail later in the article:-

  • Chlorine Levels!
  • Temperature Shock!
  • Ammonia, Nitrate, Nitrite Levels!
  • Problems With pH!
  • Phosphate Levels!
  • A Lack Of Good Bacteria!
  • Water Tannin Levels!

Some betta fish tanks can actually have problems with more than one of the potential problems above so consider all possibilities to work out exactly what’s wrong with your bettas tank.

Chlorine Levels!

Chlorine is often the number one problem that we see with people’s tanks when their bettas are lethargic after a water change.

This is due to most tap water suppliers adding chlorine to the tap water to keep it safe for human consumption but this can cause problems with your betta fish if you don’t use a tap water conditioner to remove the chlorine from your tap water prior to using it for your water change.

When you don’t use a tap water conditioner, the chlorine in your tap water can quickly build up to high levels in your tank which will then poison your betta fish and make them lethargic.

The good news is that this is an easy problem to solve, all you need to do is use a good quality tap water conditioner and our article on betta water conditioner wait times should be able to help you.

Some people do boil tap water for their betta fish and this can technically work but we feel that a tap water conditioner product will usually be the best option for most people.

Ammonia, Nitrate, Nitrite Levels!

The ammonia cycle is a process that all fishkeepers need to be aware of as it can cause problems with your fish if not managed correctly.

The ammonia cycle is caused by the fish waste in your tank breaking down into ammonia which is then converted into nitrate by good bacteria in your tank.

This good bacteria usually grows on surfaces in your tank such as gravel or decorations but it can also grow in your filter.

The nitrate is then broken down into nitrite by different bacteria and finally, the nitrite is converted into harmless nitrogen gas by more good bacteria.

This is why it’s so important to have a good amount of gravel or other surfaces in your tank for the good bacteria to grow on.

Although the majority of fish keepers will do regular water changes to avoid issues with the ammonia cycle in their tank, if you have a large amount of betta fish poop in the tank, the levels of ammonia can quickly build up again.

In addition to being lethargic, your pet betta fish will often also be twitching too if this is the problem with your aquarium water helping you work out the potential problems.

Water Tannin Levels!

Water tannins are common in betta fish tanks due to the natural betta habitat having a large number of tannins in the water.

Although many people avoid using tannins due to it turning the water brown or giving it a tint, they are becoming increasingly popular for betta tanks.

Tannin levels can be much lower than usual directly after a water change and this can sometimes cause a betta fish that is used to high levels of tannins in its tank to be lethargic until the tannis are replenished.

Our article going over using tannins for betta fish should be able to help you with this but most people use an in tank tannin source such as leaves or driftwood so they will naturally replenish over the coming days.

Temperature Shock!

Betta fish are tropical fish and need to be kept in water that is between 76 and 82 degrees Fahrenheit, although 78 degrees Fahrenheit is often seen as the perfect temperature for bettas.

If the temperature of your tank drops below 76 degrees Fahrenheit, it can start to cause problems with your betta fish such as making them lethargic.

Many people simply prep their new water for their bettas tank during a water change and then add the water to the tank without trying to temperature match the water.

This can cause the water temperature in the tank to rapidly decline and have problems so always do your best to avoid this.

Problems With pH!

There are a lot of different opinions out there on what the perfect pH level is for betta fish but we feel that a pH level between 6.8 and 7.4 is usually the sweet spot.

The main thing you need to avoid is having a sudden change in your tank’s pH level as this can cause all sorts of problems for your betta fish.

One of the most common problems that we see with bettas is that their owner will do a water change and then not realize that the new water they added has a completely different pH to the old water.

This can cause all sorts of problems for your fish such as making them lethargic and even causing them to go into shock.

If you are going to do a water change, always test the pH of the new water before you add it to your tank and try to match it as closely as possible to the old water.

Phosphate Levels!

Phosphates are often added to betta tanks in the form of phosphate rich foods such as bloodworms or brine shrimp.

Although a small amount of phosphate is not going to cause any problems for your fish, if the levels get too high, it can start to have an effect on their health.

Some water sources may have phosphates in them and this can spike the overall phosphate levels in your tank and cause your betta to become lethargic.

A Lack Of Good Bacteria!

Bacteria are an important part of any aquarium and without a good amount of them, your tank can quickly start to fall apart.

One of the most common problems we see with betta tanks is that they do not have enough good bacteria to process all of the waste that is produced by the fish.

This can lead to high levels of ammonia and nitrites which can both cause your betta fish to become lethargic.

A large water chance can cause problems with maintaining a suitable population of good bacteria in your tank so reducing the amount of water that you change with each water change to a maximum of 20% should prevent problems in the future.