Enlarged gill lining (pic)

[Lady Hobbs]

I put this in the disease section for lack of knowing just where to post it but what would make this gill lining protrude like this? He acts just fine, his color shows no stress and he is eating well but this gill lining is beginning to really get large and stick out.

(No, I will not add salt. I have plants in the tank.)

[Lady Hobbs]

To add: These fish have never been in an uncycled tank. Never had ammonia or nitrites and the nitrates are nearly undetectable. 50-60% water changes weekly.

[Crispy]

To add: These fish have never been in an uncycled tank. Never had ammonia or nitrites and the nitrates are nearly undetectable. 50-60% water changes weekly.

I would have said gill-curl from possible ammonia burns, but your params are too clean. almost looks like a slight deformity in the fish (as parrots are prone to). has this fish just developed this or had it for awhile?

[Lady Hobbs]

She has always had more gill movement than the others but has always been healthy and acted just fine. It's only been in the last four days that I noticed the lining like that.