Changing Water for Betta Fish: The Complete Guide

For betta fish owners, changing the water in your fish tank is essential to keeping your aquatic friend happy and healthy. But questions may arise around how often to change the water, the best method, how much to change at a time, and more. This comprehensive guide aims to provide all the information you need to become an expert on betta fish water changes.

We’ll cover everything from the reasons you need to change the water, recommended changing frequency, step-by-step instructions for filtered and unfiltered tanks, what to do if your fish gets sick after a water change, common mistakes to avoid, and frequently asked questions. Read on for pro tips and advice from experienced betta fish keepers to help you master this crucial aspect of betta care.

Why You Should Change Your Betta’s Water

Changing the water in your betta’s tank serves several important purposes:

  • Removes waste – As fish swim in water, they produce ammonia as waste. This builds up over time and can be toxic. Changing water helps dilute and remove this waste.
  • Lowers nitrate – In addition to ammonia, another byproduct of waste is nitrate. Both are toxic to fish in high quantities. Water changes keep nitrate levels in check.
  • Replenishes oxygen – Stagnant water has less oxygen. Replacing some old water with fresh water helps increase oxygen for your betta.
  • Controls pH – Tap water can influence pH. Partial water changes prevent rapid pH shifts that could stress your fish.
  • Cleans the tank – Changing water is a chance to siphon debris from the gravel and wash decorations. This keeps the tank environment pristine.

The takeaway? Don’t skip water changes! They reduce toxins and provide your betta with clean, healthy water.

Recommended Frequency for Water Changes

Now that you know why water changes matter, how often should you actually do them? Here are some general guidelines:

  • Unfiltered tanks – At least 2-3 partial weekly changes are recommended. These tanks build up waste quickly since there is no filter.
  • Filtered tanks – Once a week is usually sufficient for filtered tanks. The filter helps process waste between changes.
  • 1-2 gallon tanks – These small tanks need 2-3 weekly changes, even with a filter. The water conditions deteriorate rapidly in smaller volumes.
  • 3-5 gallon tanks – Change around 25% of the water once per week if you have a filter.
  • Over 5 gallons – 20-30% every 1-2 weeks is fine for larger filtered tanks.

The actual frequency can vary based on factors like tank size, stocking level, and how heavily your betta is fed. Get to know your tank and adjust as needed for cleanliness.

How to Change Your Betta’s Water without a Siphon

Don’t have a gravel vacuum siphon? Not a problem. Here is a simple method for changing your betta’s water without this handy tool:

Supplies Needed:

  • A small cup or turkey baster
  • A bucket or large container
  • Fresh dechlorinated water, ideally pre-heated to tank temperature
  • Water conditioner
  • Thermometer
  • Net


  1. Test the temperature of the tank water with the thermometer. Note this – you’ll want the new water to match it.
  2. Prepare your fresh water. If using tap, add water conditioner as instructed on the bottle. Heat or cool to match the tank’s current temperature.
  3. Use the net to gently move your betta into the bucket or a holding container. Temporarily removing them prevents escape.
  4. Use the cup/turkey baster to remove the old water manually. Take out the desired percentage being changed.
  5. Slowly add the new water, pouring it gently along the sides of the tank to avoid disturbing substrate.
  6. Use the thermometer to verify the new water is the same temp before returning your betta to the tank.
  7. Consider adding a bacterial supplement like Seachem Stability to help maintain the nitrogen cycle.

This method allows you to change water without the need for any special equipment cleanly. The key is ensuring the parameters – especially temperature – are the same when refilling so you don’t shock your fish.

To Change 100% of Your Betta’s Water: Yay or Nay?

Some betta owners wonder if doing a 100% full water change is advisable or if it could harm their fish. So what’s the verdict?

The risks of a 100% change are:

  • Temperature shock if new water doesn’t match old water precisely. Bettas prefer steady temps.
  • Removing the beneficial bacteria that processes waste and converts ammonia/nitrite into less toxic nitrate.
  • Potentially altering the pH drastically if tap water parameters differ from the tank.
  • Stress to the fish from being moved and having environment completely changed.

Because of these risks, most experts caution against doing 100% water changes except in special cases. Partial water changes are safer and disrupt the tank environment less.

However, a 100% change can be warranted if:

  • The fish is suffering from multiple diseases/infections. Completely sterilizing the tank may help eliminate illness-causing organisms.
  • The tank water is extremely poor quality with high ammonia/nitrites approaching lethal levels. In this case a 100% change provides immediate relief.
  • You need to disinfect and sterilize the tank after a disease outbreak completely.

If attempting a 100% change, take extra care to closely match the water conditions and minimize stress on your betta. And avoid making it a regular thing. Stick to partial water changes for routine maintenance.

How to Change Water in a Filtered Betta Tank

If your betta tank has a filter, you have an advantage in the form of water-changing tools like gravel vacuum siphons. Here is a step-by-step guide:

Supplies Needed:

  • Gravel vacuum with tubing
  • Bucket for removed water
  • Fresh treated water, heated to match tank temp
  • Water conditioner
  • Thermometer
  • Net


  1. Unplug filter and heater. No need to remove them from the tank.
  2. Use the net to move your betta into a holding container or bucket.
  3. Start the siphon by filling the tubing with water and getting a flow going. Place the siphon end in the substrate and hold the bucket below the output end.
  4. Gently move the siphon across the tank bottom, disturbing the gravel slightly to pull up debris. Continue until you’ve removed the desired percentage of water.
  5. Replace the old water with fresh water that has been conditioned and temperature-matched. Pour slowly and aim for tank walls.
  6. Double-check parameters like temp before adding your betta back to the tank. Consider adding supplements to replenish beneficial bacteria.
  7. Plug filter and heater back in.

Using a gravel vacuum makes water changes much easier by removing waste directly from the substrate while siphoning old water. Just be careful not to overdo the siphoning and accidentally remove too much water!

What to Do if Your Betta Gets Sick After a Water Change

Nothing worries more than seeing your betta acting stressed or falling ill after a water change. If this occurs, remain calm and systematically consider what may have caused the problem:

  • Was there a temperature discrepancy between old and new water? Matching the temp is crucial to avoid shock.
  • Did you use a new conditioner product or accidentally overdose? Some ingredients can be irritating.
  • Could something have contaminated the replacement water? Always use clean buckets/hoses.
  • Did you change too much water at once? Large fluctuations in parameters can be stressful.
  • Is there a water quality issue like a nitrogen cycle crash? Test ammonia, nitrite, nitrate.
  • Does harassment from tankmates stress the fish after being reintroduced?

If you can’t find an underlying issue, do smaller, more frequent water changes while monitoring water parameters closely. Use Indian Almond leaves or supplements like StressGuard to help calm your betta’s nerves while troubleshooting. Don’t give up!

Mistakes to Avoid When Changing Your Betta’s Water

Making errors when changing your fish’s water can have disastrous results. Be sure to avoid these common pitfalls:

  • Not conditioning new water – Tap contains chlorine/chloramines which are highly toxic to fish. Always use water conditioner.
  • Mismatched temperatures – The #1 cause of shock is new water that’s too hot or cold. Invest in a thermometer.
  • Infrequent changes in unfiltered tanks – Waste accumulates quickly without a filter, necessitating more frequent water swaps.
  • Changing too much at once – Stick to 25-50% max for most changes. Anything above 75% can be highly disruptive.
  • Forgetting de-chlorinator after a water top-off – Even topping up due to evaporation requires conditioner.
  • Not allowing proper tank reacclimation – After a water change, let the tank sit for at least 15 minutes before reintroducing your betta.
  • Skipping gravel vacuuming – Water changes present the perfect opportunity to deep clean the substrate.
  • Forgetting bacterial supplements – Consider products like Seachem Stability to replenish beneficial bacteria after siphoning.
  • Using soap or chemicals to clean decor – Avoid anything other than water and elbow grease on tank items.
  • Letting water parameters wildly fluctuate – Test for ammonia, nitrites, and nitrate. Aim to keep these stable.

By being vigilant and avoiding these common errors, you can master safe, stress-free water changes for your fish.

Frequently Asked Questions

Let’s answer some common questions about changing betta water:

How do I change water in a 1-gallon betta tank?

In very small tanks under 3 gallons, conduct 2-3 partial water changes per week. Use a cup to manually remove and replace 30-50% of the water during each change. Match temps and use conditioner.

What is the best water conditioner for bettas?

Seachem Prime is a popular and effective choice, as is API Stress Coat. Look for conditioners that detoxify ammonia and also provide slime coat protection.

Can I use distilled water for betta fish?

Pure distilled water lacks beneficial minerals, so it is not ideal. However, you can mix 25% distilled with 75% conditioned tap water if your tap water is extremely hard.

How do you clean a betta fish tank with no filter?

Without a filter, you’ll have to manually rely on frequent partial water changes to remove waste. Use a gravel vacuum to deep clean substrate at least monthly.

Why is my betta gasping after water change?

Gasping after a change could indicate an issue like temperature shock or exposure to chlorine. Ensure the new water parameters precisely match the tank.

Should I wash my betta fish tank decorations?

Yes, wash decor in tank water rather than tap during water changes to remove loose debris or algae buildup. This helps keep the tank clean.

Can I change my betta’s water every 2 weeks?

For filtered tanks over 5 gallons, biweekly changes are fine. But anything under 5 gallons will need 1-2 weekly changes to maintain water quality.

How much water should you take out of a betta fish tank?

For routine changes, 25-50% is a good target. Make sure not to overdo it – taking out over 75% risks disrupting the nitrogen cycle.

Should I clean my betta fish’s gravel?

Definitely. Using a gravel vacuum during water changes to clean debris from substrate helps reduce waste buildup. Just don’t deep clean all at once.

How do I clean my betta fish tank with plants?

Gently wipe plant leaves with a soft cloth or brush during tank maintenance. Avoid removing healthy plants or disturbing roots during gravel vacuuming.


Changing your betta fish’s water does not need to be a daunting or confusing chore. Following this guide makes it easy to boost your aquatic pet’s health through regular partial water changes.

The keys are using proper supplies, matching water parameters like temperature, changing enough water to remove waste without overdoing it, and avoiding common mistakes. Mastering water changes takes practice, but is fundamental to raising healthy, thriving bettas. Remember- partial water changes are nearly always preferable to complete revamps when in doubt.

You can perfect your process by understanding why water changes are vital and implementing these best practices for changing water with or without filters.