I think I have just a common Pleco, he lives in a 55 gallon tank with Iranian reds male and female, a school of tiger barbs and one rainbow shark. He has been acting strangely for the past 3 days or so. His usual behaviour is to hang out around the bottom and behind the inlet for the on the back filter. When I feed the rest of the fish he jets to the bottom to catch scraps, and I feed him 1 algae wafer a night which he usually shares with the shark. In the past few days he has been hanging out at the top of the tank at night and gulping lots of air. He isnt interested in the algae wafers for the most part but it seems that he is searching on the glass for algae to eat (I regularly clean the tank so there is little to no algae on the sides). He will gulp some air and sit on the bottom and after 10 minutes or so he will burp up the air and go and get some more. His poop is not the usual green ropes with consistent color but it is clear and stringy with green blobs. Those are they symptoms now I will try to tell you what is normal. He does not have rapid breathing it is even and normal (being relatively a novice with fish I use breath rate as a gauge of health) except when he is burping the air. He does not have a swollen belly, he has not had a belly at all since I bought him as a finger length fish and now he is about 8.5 inches long. He has no growths or spots etc on his body, his eyes look normal as well. He has no blood spots around his anus that I can see, he is a dark color so it is hard to tell. He has no growths on his mouth either. He is also not clamping his fins. From what I can tell he is quite active for a pleco to begin with he swims around all day and night searching for food.
Finally I did test the water. It has 0 ammonia 0 of nitrate (or nitrite whichever the middle chemical in the bio filter) and barely registering of nitrite. I change about 30% of the water every 10 days.
That is all I can think of that will be helpful beside the water temp is 79 degrees. Any and all help appreciated, I pride myself on having very few dead fish in my first tank
