Bettas Tail Shortening?

[biagiobird]

i noticed recently my bettas tail has gotten significantly shorter, and is all around looking less healthy. hes kept in a 5 gallon tank with a heater, no tank mates, and no filter (he disliked the current it made). i don't know the water stats, and dont have a kit for checking them. ive had him for 6 months, but do not know how old he is. hes eating and swimming fine, with no signs of distress or mood change. (note: his water is green tinted due to medication i gave him yesterday in case its fin rot, which was Jungle 'Fungus Clear')
 

 
 
compared to this photo from 20 days ago, hes lost almost half of his tail
 

 
im also concerned about the spots on his bottom fin, though hes had those all the 6 months ive had him. 
im pretty new to fish keeping, and though i try to read as much as i can and do whatever i can to keep my fish happy, i admit to not knowing enough to easily identify and treat illness well. any help would be greatly appreciated, im very attached to this little guy :c

 

[Mamashack]

to TFF, biagiobird! Sorry your betta is having problems.
He could be exhibiting signs of extreme stress if you are not filtering the water or testing the water levels for toxins.
He could be eating his own tail or as you've already mentioned could have tail/finrot.
You really should be monitoring the water particularly if it's not filtered and doing water changes very frequently according to the results.
My advice would be to do a big water change immediately and invest in water test kits and use them!
Water quality is extremely important despite what popular urban legend says about these fish. They cannot thrive in filthy water, they may not even survive if it continues for any length of time.
Get the basic 4 - ammonia, nitrite, nitrate and pH - probably cheaper in a master test kit which includes all of those. API seems to be the one most members use altho there are others out there.
Good luck!

 

[PrairieSunflower]

You can also do things to break the current the filter creates so he won't be struggling to swim.

 

[Wildbetta]

With how level and even the edge on his tail looks, I would say he is biting it himself.  Main thing is to keep his water as clean and warm as possible to allow him to heal.  A few questions though:
 
You say that there is a heater in his tank, what is the water temperature taken from a thermometer?
How often are you changing his water?
How much water each water change are you changing out?
What are you feeding him and how often?
Can you get a full tank shot so we can see what if anything might be stressing him?

 

[BettaBrightEyes]

Bettas are known to be tail biters if they are stressed, or even bored.
I had one that constantly did it to himself, and it's important to keep the water clean so his self inflicting wounds can heal with no problems. I suggest buying a filter, with either adjustable water flow or with a low water flow so he is not bothered by the current. There are many out there for low prices. This can help with his stress, because maybe the dirty water is not as comfortable as he makes it to be.
With no filter, you should be changing the water at most every 3 days, if not more often.
The temperature should also be between 76 and 82 F. That's ideal, or what I like to call, the "Safe Zone."

As for the tail biting, I suggest maybe adding caves (I use mini terracotta pots and caves made out of leaning rocks I found at the park- which were boiled before being added to the tank to kill any germs) and other plants, and even rearranging the tank for him. By doing this, you make it more cosy for him (in case he is stressed) and it peaks his interest (in case it's boredom).By giving him places to hide you also give him places to rest.
Maybe add some tank mates, such as tetras, to void his interest.

My boy Flounder loves his caves, and he seems happier now that he isn't tail biting any more.