• Skip to main content
  • Skip to primary sidebar
  • Home
  • Bettas 101
    • Acclimation
    • All About Water
      • Nitrogen Cycle
      • Ph & Ammonia
      • Water Changes
    • Betta Fish Anatomy
    • Betta Vases
    • Choosing a Tank
    • Feeding Bettas
      • Food Myths
      • Frozen & Live Betta Food
    • Tankmates for Bettas
      • African Dwarf Frogs & Bettas
      • Apple Snails & Bettas
      • Neon Tetras & Bettas
      • Otocinclus Catfish & Bettas
      • Quarantine New Fish
    • Plakat Betta
    • Rosetail Betta
    • Veil-tail Betta
  • Sick Betta
    • Diseases and Treatment
    • Aging Bettas
    • Bloating and Constipation
    • Cotton Wool Disease
    • Dropsy
    • Fin Rot and Fin Loss
    • First Steps
    • Gill Hyperplasia
    • Ich
    • Popeye
    • Septicemia (Infection)
    • Swim Bladder Disorder
    • Sick Betta Symptom Checker
    • Velvet Disease
    • Wounded Betta
    • Fish Tank Granuloma
  • Behavior
    • Bubble Nests
    • Skittish Bettas
    • Tail Biting
  • Breeding Bettas
  • Equipment
  • Q & A
  • Other fish
  • Contact

Fish Care

Everything You Need to Know About Betta Fish

You are here: Home / Bettas 101 / All About Water / Water Changes

Water Changes

There are several variables that affect how often you should change your betta’s water and the only true way to tell is to test your water with the appropriate aquarium test kits.

We change our betta’s water mainly for the reason that toxins accumulate over time that are extremely harmful to aquarium fish. These toxins are mainly ammonia, nitrite and nitrate, and are the byproducts of fish waste and decaying debris like food and dying plants. Ammonia and nitrite are the most dangerous and any accumulation of these toxins can lead to illness or even death. Nitrate, a waste product of bacteria in the water, is the least dangerous but can become toxic at high concentrations. To understand more about these compounds, visit All About Water.

Now that we know WHY we change our betta’s water let’s look at the variables that affect how quickly those toxins accumulate.

Tank Size:

Toxins will reach dangerous levels much faster in a small volume of water then they will in a larger one. This is just simple dilution. Imagine you have a dropper full of food coloring. A few drops in a bathtub full of water would hardly be noticeable at all, but add the same number of drops to a small glass and it would be quite noticeable. This is one of the main reasons that larger tanks are recommended for beginners while smaller ones are often considered to be more appropriate for advanced hobbyists. Many folks new to the hobby don’t realize this and think it will be easier for them to start with a small tank.

Cycling:

Photo by Clay Mask

The Nitrogen Cycle is a naturally occurring process where beneficial bacteria grow and reproduce to consume the toxins produced by fish and decaying matter. This process has occurred all over the world in lakes, ponds, streams and oceans and will also occur in your aquarium if given the chance. Experienced aquarists usually monitor this process when they first set up their tanks. The cycling process itself can be quite stressful to fish but once it’s complete it creates a safer and more stable environment. An uncycled tank doesn’t yet have the bacteria in place to consume toxins and frequent water changes may be necessary to keep ammonia from building up. If you plan to cycle your tank you will have to stop performing full water changes. Once the process is completed, partial 25% water changes are all that is necessary to keep toxins at bay under most circumstances. To learn more about tank cycling visit Tank Cycling: The Fishless Method. Let’s assume, for now, that your tank is not cycled…

Fish Waste:

Fish waste is the main contributor to toxins in the water. Ammonia, which is severely toxic at even minute levels, builds as fish defecate and urinate. The rate at which these levels raise depend on the fish. Like humans, fish metabolize their food at different rates based on age, size and genetics. Water temperature may also affect how quickly fish produce waste. A betta’s metabolism will be faster in warmer water then it will be in cooler water.

Decaying Matter:

Uneaten food is another major contributor to ammonia build up. Food left to breakdown in the tank will quickly add to the toxicity levels. To avoid this, try not to overfeed your fish and remove any uneaten food within about 10 minutes of feeding. Also, the type of foods you feed may contribute to toxin build-up differently.

Plants:

Plants can work for you or against you. Healthy plants will utilize some of the toxins produced in the tank and though they can’t replace water changes, they can help reduce the frequency you need to change your water. On the contrary, however, dead or dying plants will breakdown producing more deadly ammonia. Learn the needs of the plants you buy and remove any dead leaves to get the most out of your planted aquarium.

Bioload:

The quantity, size and species of the fish you keep determine your bioload, or the amount of “life” you can safely support in a given size tank. It’s difficult to quantify but a common calculation is one inch of fish per one U.S. gallon of water. If a grown female betta is 2.5 inches in length approximately, and you wanted 4 of them then you would need a minimum of 10 gal to support the bioload. (2.5 in x 4 fish = 10 gal) In reality there are so many other things at play, like the physical mass of the fish, their behavior and how they eat. For instance, you would never keep four male bettas in a 10 gallon tank because they are too aggressive and you would never keep four, 2.5 inch goldfish in a 10 gallon tank because they produce significantly more waste then your average hobby fish. Basically, for your purposes, remember the more fish you have in your aquarium, the quicker toxins will build and the more frequently you will need to perform your water changes.

Filtration:

The type of filtering system you have in your tank and how it is maintained will also affect your toxin levels. A suitable power filter with charcoal media may remove more waste then a simpler sponge filter.

Substrate:

Toxins may accumulate at a different rate depending on the type of substrate you use in your tank. A tank with a deep sandy bottom may hold more decaying matter then one with large gravel. Larger substrate may be cleaned easier with a siphon then smaller particles. A bare bottom tank, though less attractive, is often the easiest to clean.

What does all this mean?

Photo by Irina Souiki

Ok, now you know there is no simple answer as to how often you should clean your betta tank. Still, you need some direction. Fortunately, there is a good way to determine your individual cleaning schedule. Let’s assume, again, that your tank is uncycled and you will be performing regular full water changes. To determine how often you need to change your water start by doing a complete 100% water change, essentially starting from scratch. Treat the water with a good dechlorinator like Kordon’s AmQuel+ and NovAqua. Acclimate your betta and begin testing your water for ammonia starting that day. Be sure you are using a good aquarium test kit. Ammonia kits that come with a reagent bottle (or two) and a test tube are far more reliable then the dry dip-stick test kits. Be sure to purchase a “Salicylate” test kit rather then a “Nessler” test kit. In a Salicylate kit the color comparison chart is often green while the Nessler kit measures in shades of amber.

The first day you measure the ammonia levels should read 0. Continue to measure each day until trace amounts of ammonia become visible. As soon as you see ammonia you know exactly the maximum number of days you can go between water changes. If it takes 6 days for ammonia to present itself you should be doing full water changes every 5 days to avoid any measurable ammonia build-up. If it takes 10 days for your test to show ammonia, then you should do that water change by the 9th day at the latest. If you make any significant changes to your set up (I.e. add a new fish or significantly change the diet) repeat the test to be sure your water changing regimen doesn’t need a change itself.


Primary Sidebar

Search


Recent Posts

  • Cool Betta Fish Tank Ideas
  • How Long Do Betta Fish Live For? – 5 Helpful Tips For a Long and Happy Life
  • 3 Gallon Fish Tank for Betta
  • 10 Gallon Aquarium Stands and Cabinets
  • How Much Do Betta Fish Cost to Buy and Care For?

NippyFish Facebook Page

Visit the NippyFish Facebook Page

Featured Posts

Complete Guide to Betta Fish Diseases and Treatment

This complete guide on Betta fish illnesses and diseases from A-Z will help you pinpoint what is wrong with your Betta and how to treat it.

The 4 Most Common Signs of Illness in Betta Fish

This article focuses on the 4 most common signs of illness in Betta fish.

Betta Fish Tank Setup – A Detailed Guide For Beginners

This article will be providing a detailed beginners guide on how to setup a tank for your Betta fish.

Top 12 Betta Fish Toys

This article has a list of some of our favorite Betta fish toys. Don’t have a bored Betta.

Setup an Aquatic Plant Environment For Your Betta

Having a healthy plant in your tank will help to improve the water quality by filtering out waste and removing some of the CO2 that’s produced by your fish.

Copyright © 2025 All Rights Reserved | NippyFish | Privacy Policy

Nippyfish.net is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to amazon.com.