Betta finrot - no ammonia traces?

[Super Nova]

Hello,
I’ve had a male betta for 8 weeks now, he’s had finrot previously but I’ve managed to heal him since then. Recently i did however notice his fins have had holes in them again, I moved him from a 5gal to a 15gal tank with a much stronger filter. I’ve had 0 traces of ammonia in both tanks for a stable time. This therefore crosses out that ammonia was the cause of his finrot, I’m a bit concerned it might be because of the strong current the filter creates. I have it set on the lowest settings and I can tell he struggles in it.. however my little pretty boy still swims in it, even though he’s got plenty of room in the tank to avoid the current so I’m not too sure what might be happening. Also I’ve noticed him starting to create bubbles at the surface of the water - which I’m guessing is his nest (it’s pretty cute watching him build it actually)

Im hoping someone could tell me what I can do to help him, I’ve heard people reducing the current by using a plastic bottle but I’d rather get some advice before modifying my filter and somehow killing it.
Thank you!

 

[NickAu]

I’m a bit concerned it might be because of the strong current the filter creates. , I’m a bit concerned it might be because of the strong current the filter creates. however my little pretty boy still swims in it

You must do something to cut the current down, he is struggling in the current and thats causing stress, Its no good for him.

Tell me about your tank. The 5 gal.

Is it cycled
is it heated
What is the water temp
How often do you change water
How much do you change
What water conditioner do you use
Has the tank got any plants?
How often do you feed him
How much do you feed him
What do you feed him

Finrot is the direct result of poor tank conditions.

 

[Super Nova]

I changed the tank recently, I used things (substrate, decorations, filter ect) from my old one in my new one so it’s going through a mini cycle right now, but there are no ammonia traces. My temperature is at about 76 Fahrenheit, I only have two moss balls, I feed him a little bit in the morning and a little in the evening. I feed him TetraMin. I change the water every 4 days, only about 25% and I use interpet tap safe to dechlorinate my tap water.
My 5 gal tank;
I changed 80% of the water every 2-3 days and pretty much everything else was the same.