gill curl

[Aro77]

Hi, i have this big red which is about 33 - 34 inches in size, he is currently in a comm of snow gars, he eats full body kunning ( never cut with bone etc ) and is still eating well and greedily. On Saturday i noticed him breathing harder than usual by opening and closing mouth, today i have noticed the soft gill curling on one side, along with swimming very slightly slanted and will go back straight after awhile. as well as going near the water surface occationally looking hungry which he does do quite often but in this case his top body would slightly go above the water surface before he would swim back down and do his usual stuff. is it possible he might have some air stuck? i am starting to do 25% water changes every 2 days as well as clean the filter to help improve the water. PH and ammonia is fine at around 7.2 and 0 respectively but i do suspect a super high nitrate level as i do not change water often for this tank as the bioload is considerably low, however i do top up about 3L of water everyday for the filter compartment


i will try to upload a clip soon