Help - betta breathing heavy/fast on bottom of tank

[BAT]

Nerms-

I moved by betta to a QT tank Tuesday because I was having problems with high nitrites and an ammonia bump (0.5). I noticed some blackening of his dorsal fin so decided to move him early. He had a bad case of fin rot back in December so I decided to jump on it this time. 

Since I moved him he has been hiding at the bottom of the tank in the past 3 days and not eating. His last meal was a big bloodworm meal which may have been a source of the problem.  

He hasn’t been eating and when he does come out he zooms around and then goes back. 
 

Now he looks like he is breathing heavily. The gills look like they are moving at a rate of 75-85 per minute (estimate). I don’t see any spots but it’s hard to see him bc he is hiding in a cave. 

I started kanaplex this afternoon. salt is at about 1 tbsp to 2 gallon. Temp 80.5. Amm 0 nitrite 0 nitrate 0

there is an AC sponge filter in the water. 
 

Thoughts?

Edited April 18, 2022 by BAT

[ange]

Gasping at the top of the tank is almost always a sign that the water has a low volume of dissolved oxygen. Increasing the flow on your sponge filter to facilitate more surface agitation and a water change can help in event of deoxygenation. Many medications and water conditioners can contribute to this.

[BAT]

I increased the flow of the sponge filter. I can add another air stone. 
 

I am wondering if this could be gill flukes?

[BAT]

I started ich X yeast night and general cure just now. He finally came out this morning during a water change (before I added general cure) and he ate some food. 
 

there was a lot of white floating gunk in the water and the filter had a white coating all over it. See pic. Is this slime coat?

[quikv6]

That gunk looks like residual medicine. Did you just dump the General Cure packet in? If so, in my opinion, it's better to dissolve it is a small cup of tank water first, then dump the contents of the cup in the tank.

[BAT]

That gunk was before I put the general cure in. I had put kanaplex in the day before but I have done that in the past and not seen that.