Holey Fins?

[Wildbetta]

Ok well that explains the problems you have been having with both of your tanks.  With the 20 gallon that had an established cycled filter, it ended up producing more nitrAtes in reaction to the constant addition of ammonia with each water change.  In the 3 gallon with an uncycled filter -- it led to a disastrous and deadly mess.  First thing I suggest (and I can not believe I forgot to mention it before) is to take some media from your 20 gallon tank's filter and put it in the 3 gallon tank's filter.  That will help a little but you will still have to be diligent with water changes every other day or even every day to keep all the levels "safe".  I also suggest double dosing the Prime to help with the ammonia as well in the 3 gallon.  I would talk to your water provider and find out if they have changed anything around which could be causing the ammonia in the tap water.  Running purigen in your filters should help with the ammonia in the 3 gallon and nitrAtes in the 20 gallon and might be your best long term "solution".

 

[Hollyweb]

Ok well that explains the problems you have been having with both of your tanks.  With the 20 gallon that had an established cycled filter, it ended up producing more nitrAtes in reaction to the constant addition of ammonia with each water change.  In the 3 gallon with an uncycled filter -- it led to a disastrous and deadly mess.  First thing I suggest (and I can not believe I forgot to mention it before) is to take some media from your 20 gallon tank's filter and put it in the 3 gallon tank's filter.  That will help a little but you will still have to be diligent with water changes every other day or even every day to keep all the levels "safe".  I also suggest double dosing the Prime to help with the ammonia as well in the 3 gallon.  I would talk to your water provider and find out if they have changed anything around which could be causing the ammonia in the tap water.  Running purigen in your filters should help with the ammonia in the 3 gallon and nitrAtes in the 20 gallon and might be your best long term "solution".

 Thank you, I really appreciate your help.
 
The filters that came with the 3 gallon are the closed up kind that you can't change, you just buy a new one and throw the old one away. The filter for my 20 gallon is the same except you can at least take the top plastic part off and it's basically a pouch with carbon inside.
 
I suppose at least knowing the ammonia is coming from the tap it makes me feel better in the sense that it's not anything I'm doing wrong. I felt like I was killing all my fish.

 

[Wildbetta]

I suggest in that instance that you work on replacing your filter with better media.    Bonded filter floss, cotton batting, aquarium sponges, ceramic rings, bioballs, ect are better and actually more cost efficient than the filters you have right now.  The important thing about the ones you have now is not to throw them away unless it is literally falling to pieces as that takes all your cycled bacteria with it.
 
It does make it better that it is not something that you are doing.  

 

[Hollyweb]

Here is a better picture. It has gotten worse and he is barely breathing now.