Help with Celestial Pearl Danio

[Slash]

My Celestial Pearl Danio is having trouble breathing it seems. Other CPDs are fine as are other fish. I'd had it for at least 6 months. What should I treat it with? I have Fritz ParaCleanse and Fritz Maracyn. I'm not sure what's wrong. Any ideas?

Water parameters:

Ammonia: 0

NO2: 0

NO3: 40

PH: 6.5

KH: 0

GH: 60

In a 29 gallon with 2 Honey Gouramis, a Panda Gara, 7 Habrosus Corydoras and 3 other CPD who seem fine. They are all make I believe and this one struggling is a female I think.

 

[Colu]

Have you added anything new to the tank resently has it been eating ok also I would add an extra air stone and a small amount of aquarium salt 1 table spoon for 5 gallons it helps with gill function and adds essential electrolytes to reduce stress in your fish 

Edited October 11, 2021 by Colu

[quikv6]

A KH of 0 is always a bit worrisome to me, as it can result in PH fluctuations, or a PH crash. Could that be related....possibly. I would test the tap and see what the KH is. You can use crush coral to help raise KH, and, in turn, stabilize the PH and prevent a crash.

I think adding an extra air stone would be a good idea, as well. Out of the two meds you have, I think Maracyn would be more of a broad spectrum treatment, but you may want to try some salt and an extra air stone first.