I bought two male bettas from a local pet store a little over a month ago. Actually, rescued is a better term. I also purchased a small two gallon tank with a divider down the middle. (I know that they need at least 2 gallons by themselves, but I couldn't afford a bigger one at the time.) Two weeks after bringing them home, I started noticing a black patch on my white one's side. He was eating normally (like a pig) so I wasn't too worried. But, it slowly got bigger. I can't find anything on the symptom. I did read that "marbling" does happen, but I just want to be sure. My other betta doesn't show any discoloration.
What size is your tank? I bought a new tank two days ago- 6 gallons
What temperature is your tank? No clue, new tank was supposed to come with a heater but there wasn't one in the box.
Does your tank have a filter? Yes, a whisper filter that is currently on the lowest setting.
Does your tank have an air stone or other type of aeration? A bubble stone on the opposite side of the filter.
Is your tank heated? Not currently, (working on that) water seems a bit cool to the touch.
What tank mates does your betta fish live with? Both boys are in the same tank, but I have a divider in the middle.
What type of food do you feed your betta fish? Flakes
How often do you feed your betta fish? It depends. I feed them when I wake up. If they do not eat, I dip out the food and try again when I have lunch. And before I go to bed. So roughly twice a day, but these flakes are fairly large.
How often do you perform a water change? In the old tank, every two days. I just put the boys in their new tank today.
What percentage of the water do you change when you perform a water change? Did do 75%.
What type of additives do you add to the water when you perform a water change? Dechlorinator
Have you tested your water? If so, what are the following parameters? I have not tested my water.
Symptoms and Treatment
How has your betta fish's appearance changed? See above.
How has your betta fish's behavior changed? See above.
When did you start noticing the symptoms? See above.
Have you started treating your fish? If so, how? I haven't treated for anything yet, didn't want to cause any unnecessary stress.
Does your fish have any history of being ill? Not that I know of.
How old is your fish (approximately)? I've had him for a little over a month, but before that...who knows?