Treating water for a betta fish comes down to one essential step: removing chlorine and chloramine from tap water before your fish ever touches it. A water conditioner containing sodium thiosulfate does this instantly, and it’s the only product you truly need. Beyond that, maintaining the right temperature, pH, and mineral balance keeps your betta healthy long term.
Why Tap Water Needs Treatment
Municipal water supplies add chlorine or chloramine to kill bacteria, which is great for human drinking water but lethal to fish. Chlorine concentrations as low as 0.2 to 0.3 parts per million kill most fish quickly, and even trace amounts around 0.003 ppm cause stress by damaging gill tissue. Chloramine, a combination of chlorine and ammonia, is increasingly common in city water because it lasts longer in pipes. It’s equally dangerous and slightly harder to neutralize.
Tap water can also carry heavy metals like lead and copper, especially if your home has older plumbing. Some water utilities raise the pH of their supply specifically to reduce lead leaching from pipes, which means your tap water’s chemistry can shift seasonally. A good water conditioner handles both the chlorine and the metals in one dose.
Choosing the Right Water Conditioner
Look for a conditioner that lists sodium thiosulfate as its active ingredient. This chemical neutralizes chlorine on contact, and it’s the proven workhorse behind virtually every effective water treatment product on the market. Brands package it with different marketing claims, but the active ingredient is the same.
Be cautious with products that claim to also neutralize ammonia, nitrite, or nitrate. These claims are marketing language with no real chemical basis. A sodium thiosulfate conditioner removes chlorine and chloramine, and that’s what you need it to do. Also avoid any product that relies on aloe vera alone as its dechlorinating agent. At least one widely sold “stress coat” product makes this claim, and multiple fishkeepers have reported tank wipes after trusting it as their sole water treatment.
Dosing is straightforward: most conditioners are formulated to neutralize 1 to 2 ppm of chlorine per standard dose, which covers the vast majority of municipal water supplies. Follow the dosage on your specific bottle and treat the water before adding it to the tank, not after.
Water Temperature and pH
Bettas are tropical fish native to shallow waters in Southeast Asia, where temperatures range from about 72°F to 89°F (22 to 32°C). In practice, you want to keep your tank between 76°F and 82°F, which sits comfortably in the middle of that range. A small adjustable heater is essential unless your room stays consistently warm. Temperature swings of more than a few degrees in a short period stress bettas more than a steady temperature at either end of the range.
Wild bettas live in naturally acidic water with a pH between 5.2 and 7.0. Most tap water falls between 7.0 and 8.0, which is slightly alkaline but generally tolerable for captive-bred bettas that have been raised in similar conditions for generations. Don’t chase a perfect pH number by adding chemicals. Stability matters more than hitting an exact target, and pH-adjusting products can cause dangerous swings if you’re not testing regularly.
Tap Water vs. Distilled or RO Water
Tap water is the simplest and most practical choice for betta tanks. It contains dissolved minerals your fish needs, and a basic conditioner makes it safe. The only real drawback is that tap water chemistry varies by region, so it’s worth testing yours at least once to know what you’re working with. Inexpensive test strips or a liquid test kit from any pet store will tell you your pH, hardness, and whether you have any ammonia or nitrite present.
Distilled water and reverse osmosis (RO) water have had nearly all minerals stripped out. This sounds clean, but it’s actually a problem. Bettas need trace minerals like calcium and magnesium to maintain healthy cell function and stable osmotic balance. Pure distilled water used straight will stress your fish over time. If your tap water is extremely hard or has unusually high levels of something problematic, you can mix RO water with treated tap water to dilute it. But using 100% distilled or RO water without adding minerals back (a process called remineralization) is worse than using conditioned tap water.
How Often to Change the Water
Water changes are the single most important maintenance task for any fish tank. In a filtered aquarium of 5 gallons or more, change about 10% of the water weekly or 25% every two weeks. Always treat the replacement water with conditioner before pouring it in, and try to match the temperature of the new water to the tank so your betta isn’t shocked by a sudden shift.
If you’re keeping a betta in a smaller unfiltered container (which isn’t ideal but is common), change roughly one-third of the water every 3 to 4 days. Waste products like ammonia build up much faster without a filter, and partial water changes are the only way to keep concentrations from reaching toxic levels. Never replace all the water at once. A full water change dramatically shifts the chemistry your fish has adjusted to, and the stress can be more harmful than the slightly dirty water you’re trying to fix.
Use a small siphon or turkey baster to pull water from the bottom of the tank where waste settles. Replace it with pretreated water at the same temperature, and you’re done.
Indian Almond Leaves as a Natural Addition
Many betta keepers add Indian almond leaves (also called catappa leaves) to their tanks. These dried leaves release tannins into the water, tinting it a light amber color and gradually lowering pH. For bettas, this mimics the dark, tea-stained waters of their native habitat in Thailand and surrounding regions.
The tannins have documented antibacterial and antifungal properties. They’ve been shown to inhibit the growth of pathogens that cause fin rot and other common betta diseases. The darkened water also appears to reduce stress, likely because bettas evolved in heavily shaded, tannin-rich environments and feel more secure in dimmer conditions. Indian almond leaves aren’t a replacement for a proper water conditioner, but they’re a beneficial supplement. Drop one small leaf into a 5-gallon tank and replace it as it breaks down, typically every two to three weeks.
Aquarium Salt for Health Support
Aquarium salt (not table salt, not marine salt) is a common preventative treatment in betta keeping. A mild dose of 1 teaspoon per 5 gallons acts as a general tonic, supporting gill function and helping your fish maintain a healthy slime coat. The International Betta Congress notes that many experienced breeders and shop owners keep this low concentration in their water at all times as a disease preventative.
For treating an active problem like early-stage ich or mild fin rot, some keepers increase the dose to 1 tablespoon per 5 to 7 gallons. Higher therapeutic concentrations of 1 to 3 tablespoons per gallon are used only in short dip treatments lasting a few minutes in a separate container, never in the main tank. If your betta shares a tank with live plants or other species, keep in mind that many plants and some fish (especially bottom-dwellers like corydoras) are more sensitive to salt than bettas are.
Acclimating Your Betta to New Water
When you first bring a betta home, or when moving one to a tank with different water chemistry, a slow acclimation prevents shock. The simplest method is to float the sealed bag in the tank for 15 minutes to equalize temperature, then gradually mix tank water into the bag over about two hours. Add a tablespoon of tank water every 10 minutes, removing an equal amount of bag water each time with a turkey baster so the bag doesn’t overflow.
After two hours, the water in the bag will be mostly tank water. At that point, gently net or pour your betta into the tank and discard the bag water rather than dumping it in. Pet store water often carries pathogens or medications you don’t want in your system. Keep the tank light off for the first few hours to let your betta settle in without added stress.