One day this split was just there It has not gotten bigger so I don't know what it could be. Ammonia is high (1.0 tested with liquid test kit) but was recently 2.0, I have recently started doing daily water changes to combat the ammonia. Here is a pic of My Betta flaring where you can see the split in his tail:
Tons of people have splits all over their bettas tail and other fins. Sometimes caused by using a bad net to catch them or a sharp object such as low-quality plastic plants that are present in the tank. I would not worry too much but if you care a lot make sure you don't have anything too sharp and also make sure not to use an overly-coarse net. Using a cup to catch a betta is better.
could also be the begining of tail rot due to ammonia being high. Ammonia should always be at 0. If it is not 0 then you need to be doing more water changes. The tank will not cycle if you don't have water movement due to a filter or airstone.
LOL, it is homemade and penguins are one of the only things I can draw. I got bored one night so I decided to just make the background. It's just a sheet of computer paper with penguins drawn on it.
It is really very important to keep the water clean, pristine. Many problems will develop due to ammonia and nitrites in the water. Keep his water pure and clean. Fish have remarkable recuperative powers when they are in clean pure water.
Prime is a really good water conditioner that can help with ammonia and nitrites... neutralizing those toxic by products for about 24 hours, giving you time to do the water changes you need to do.