My sick comet Lazy Jack

Question
My comet lazy jack is currently lieing on his left side on the bottom of my aquarium and is breathing un usually fast. I know he could die but I like him to much what disease or sickness could he have.   There are no other symptoms and he can move if I poke him with the net. His anus is also inlarged

Answer
lots of variables here Ben,
could have a bladder issue, could be parasitic.
if this is a new tank, there could be ammonia issues, check levels if you can.
you could have high nitrate levels if the tank is an older tank, or it could be a low ph issue as well, again test if you can, if not, perhaps your local fish shop can help.
fish may also have an intestinal issue..
check the levels first and rule that out, or in as the case may be.
if the levels are ok, then treat with a general cure that covers the symptoms, again your local shop should have the necessary meds.
isolate the fish in a quarrentine tank if you can rather than treat the main tank.
good luck with your fish and I hope he recovers.