Unfortunately, with some bettas, tail biting is a habit similar to i dunno, biting nails in little kids.
Keep his water clean, continue trying to occupy him.
Sorry if I forgot, but do you have a filter In there?
How's the lighting by his tank. If it is too bright, that might be a cause.
If he's in a quiet room, consider moving him somewhere with a lot of people traffic. If he's in a loud trafficy room, maybe bring him elsewhere.
Don't give up :) and don't worry, if after a very long time of trying different things but no success, you might just want to accept him as a wanna-be plakat. Some bettas are odd like that and bit their tails short.
I'm sorry I am in the same boat.. well I was. Ickis started chredding his tail so bad, it's not even half it's original length! He has a wonderful set up.. but it didnt help. What I found to help, and his tail hasnt gotten more chewed since, is I made his filter flow a little bit stronger and he is so happy to swim in the little current. maybe try the filter on?
Do you add anything to the water other than conditioner?
I figured out that my betta would bite his tail whenever I would add salt to help treat his already ripped up fins...from previous tail biting! I didn't figure out it was a vicious cycle until one water change I forgot to add salt.....yep.
Not all bettas bite as a result of boredom--more often than not, it is in response to a stressful situation. Changing his tank around, adding new things, and moving the tank could be adding to his problem rather than alleviating it. I always assume that the bite issue is from stress before boredom--because your attempts to alleviate boredom will only stress your fish out more.
Instead of moving him around and doing all kinds of crazy things, try dimming the lights, giving him lots of places to hide and feel secure, keep him in a low traffic area, baffle the filter flow, monitor the temperature of the tank to make sure it is stable, and acclimate him very slowly after every water change.
Some fish also do it in response to hunger. Instead of feeding him all at once--try giving him small amounts of food throughout the day. Others do it for wacky reasons. One of mine did not like to be in total darkness and stopped biting after I added a dim nightlight to the room at night. Another of my fish stopped biting when I removed a large decoration which freed up more swimming space. Figuring out what the trigger is for your fish can be a difficult process of elimination--but try not to change too many things at once. Try to limit yourself to one thing per week so you don't freak him out.
well i can't feed him just yet he is extremely bloated for some reason, i only feed him 3 pellets a day....
only conditioner in the water,
i do try to move the ornamented each week in water change day
only natural light. the tank has a light but in Canada it gets dark before im home to turn it off....