What's Up With My Betta's Tail?

[Smilefac19]

Hi,
I'm new here and I'm coming to you all for assistance with my betta. I've been trying to figure out what is up with his tail for months now. He's a crowntail betta, who lives in a 5 gallon tank that has a filter/air pump. He lives by himself and nothing in his tank is sharp or jagged. He eats and passes his food like a champ so no worries there. I keep his tank really clean, like I said weekly water changes, he is not overfed and the filter is changed when it starts getting too green with algae.
 
His tail since I got him has progressively gotten smaller and smaller. I doubted it was fin rot originally since that is usually caused by poor water conditions, and his have never been bad. I decided to start trying to treat him for fin rot anyways, but without using any medications since I wasn't sure it was indeed rot. I started changing his water every day for two weeks, then every other day, then every third day, and so on. We're back to changing it only once a week and his tail has not gotten any better or any worse. I also tried adding some aquarium salt to his water during the time I was doing frequent water changes. I have read on numerous sites that that can help with fin rot. Still nothing. It looks like some parts of his tail have grown back but other parts are still super short.
 
Any idea as to what could be going on? Or what more I could do? He acts normal, swims around a lot, etc. but this small tail has me worried.
 
Thanks all!!!
 
I've attached a pic of him and his tail. It was the best I could get of the active little bugger.

 

[bluesword23516]

He could be nipping at himself. I have heard of that before, watch him and see if you see any of that. I am not sure what to do if he did do that.

 

[Wildbetta]

First off, your betta is not a crowntail.  He is a longfin betta and depending on how far he can spread his tail open would decide on what tail type.  
 
What do you mean when you "change the filter when it gets too green with algae"?  Do you completely replace the filter media?  If so, you are harming your cycle every time you do that.  Which will throw your tank into a mini cycle.  
 
Personally your betta appears that he might be biting his own tail.  This could be from a couple of different reasons and normally stress is one of the biggest reasons.   Can you get a picture of the whole tank?

 

[Smilefac19]

I apologize, it's a 2.5 gallon tank. I mistyped.
 
I've never seen him bite at his tail.
 
I thought he was a crowntail, because that's what the store told me... *sigh* You can never trust those stores anyways. Sorry for the incorrect information. But his tail was much bigger and beautiful when I first got him. Now it's all stubby.
 
The filter in the tank is a carbon based filter and it says to replace them every 4-6 weeks. I usually replace them around 6 weeks because they don't get covered in algae or anything like that.
 
 
I previously had the same size tank with the same kind of decorations for a different betta and never experienced any difficulties. This is a new tank and new decor, but my upkeep on the tank/fish is the same...
 
Here's a pic of his whole tank:

 

[attibones]

By replacing the carbon filter, you are cycling the tank all over. Feel free to keep those carbon packs! The carbon wears off after two weeks, but bacteria can still grow in the pads. You need that bacteria to convert ammonia into relatively harmless nitrate.

There does not appear to be a heater in his tank. His water needs to be at least 80 F. If the room temp is around there, he should be fine. I don't usually run a heater with my bettas because I live in the South and my AC is broken.

You'll need to start off by getting a liquid test kit (most of us use the API freshwater master kit, as it is readily available) which tests for ammonia, nitrite, and nitrate. PH is always useful as well.

Follow the fish-in cycling guides on the top of the page for more info on how to complete a fish in cycle.

I would also like to add that your tank is on the small side for this species. There is some debate over the minimum size for bettas. The absolute lowest is 2.5 gallons (I'm more of a five gallon guy). Start by doing daily water changes (around 50%) and see how he does.

 

[Wildbetta]

Don't feel bad about the incorrect info about the tail type, that happens all the time especially when the stores can often have them mislabeled.  
 
A lot of the time bettas that bite their own tails are never seen doing it so I am not surprised that you have not seen your boy doing so.  Looking at your tank, it could very well be stress related biting.  The filter is probably a bit on the strong side for him in such a small tank, the constantly changing parameters with the filter being changed, and the lack of a heater are all things that are things that could be stressing him.
 
The decor that is in the tank, have you ran something like a piece of pantyhose/nylon over it to see if it snagged?  I know that the decor looks betta friendly but sometimes can have some rough spots that will snag a fin.  
 
I suggest you stop changing the filter inserts for a start.  Even though the carbon does not last, the rest of the insert is the important part which you need to keep.  If you think it is getting dirty, just rinse it out in old tank water once a month or so and it will be fine.  Only replace when it is literally falling apart and even then only replace it in stages so that you do not loose the beneficial bacteria on the filter.
 
I would do 50% water changes no less than every other day until you get the tank fully cycled and then you can start doing a change every 3 days or so.  
 
 
 
 
 

There does not appear to be a heater in his tank. His water needs to be at least 80 F. If the room temp is around there, he should be fine. I don't usually run a heater with my bettas because I live in the South and my AC is broken.

 

 
 Sorry Atti, but I do have to disagree just a little here.  A betta tank needs a heater unless you have a room that stays no cooler than about 82F which would put water temp at around 80F.  I am in the south and even without a heater (in my garage with no AC) my tanks rarely get to 80F during the day and that is with the temperature outside reaching close to 100F.  The issue comes in at night when the temperature drops in the room (unless you have a temperature controlled room) which will cause the water temperature to drop.  These fluctuations can cause stress in most individuals.  It is also important to have a heater in the tank so that you can raise the temperature when needed.  The treatment that I recommend for finrot and most other issues starts with very clean water and bumping the temperature in the tank up to 82-84F.  And treatment for ICH and velvet would require the temperature to be raised to at least 86F.

 

[Smilefac19]

I've checked the decor and it doesn't snag. His tank isn't the biggest, I know but I didn't think it was too small... He is at my desk at work so I can't go too big with the tank.

It doesn't have a built in heater but the lightbulb in the overhead part of the tank keeps the temperature around 82. I have a little thermostat for it because I was worried about the lack of a heater in the beginning.

I'll start changing the water as you recommended.

I just want him to be healthy. But having a stubby tail doesn't seem healthy, even though he acts happy.