Your Betta can become sick from many different situations. If the water in your fish tank is too warm or too cold, it can severely affect them. Or perhaps there is chlorine in the aquarium water or another chemical that is toxic to your Betta. Also, many diseases are caused by various catalysts within your aquarium.
In the wild, Bettas can tolerate a wider range of temperatures. In your home aquarium, they prefer a warmer temperature. Some hobbyists and Betta experts disagree, but most profess that water temperatures between 76 and 82 degrees Fahrenheit is optimal.
Most public water systems in the United States add chlorine to fight bacteria that might be present. That small addition to your home water supply is, in itself, the greatest killer of aquarium fish. Although some hobbyists state that if you let tap water stand in the open air for at least 48 hours, the chorine will evaporate. Unfortunately, that isn’t always true. To be completely safe, it’s best to by a commercial dechlorinator that includes both sodium thiosulfate as well as ammonia removers.
Normally, your Betta is adapted to a lower pH value. Although some can tolerate up to a 7.8, it’s highly dangerous to allow untreated tap water to touch your Betta. With a pH of up to 10 and higher, this is unhealthy for your fish. Ask your fish dealer or pet store owner for a test kit to measure your water’s pH and purchase the substance that will bring it to the correct level.
Viruses can come through a variety of means: unwashed rocks and decorations, uneaten and rotting food and from other fish newly added to the aquarium. Although anti-viral drugs for fish are being tested, the only current solution is to keep changing the water in the tank and quarantining the sick fish.
With over 35 groups of bacteria types, it’s difficult to keep these bugs completely out of your aquarium. And while some are harmful to your Betta, most of the bacteria in your fish tank are useful. If you notice that your fish is lethargic, is hiding, has spots and/or wounds on his body, has any fin or tail rot, or he isn’t eating, he could be infected with several different kinds of bacteria. Usually several changes of water can put a quick end to a bacterial tank situation because it allows the Betta’s immune system to recover.