Hi -- anybody have some thoughts about a healthy, 4 year old Red Oscar who has stopped eating, and has developed a large, round growth on the bottom of its body, just before the anus. It is shaped like the bubble machine-gun turrets on the bottom fuselage of a WWII bomber. Seems to be getting bigger. Fish has been lethargic for a few days, with its back to us, but is now moody/ grumpy and occasionally aggressive with its similar sized 4-year old Oscar mate. Might be a blockage or intestinal parasite?? Water specs are adhered to religiously ... an established 90 gallon tank with good equipment and weekly 25% changes and testing. Diet has been hi-quality pellets, frozen bloodworm and shrimp, as well as insects and worms from garden. Yes, I admit it, the Oscar stopped eating and developed the roundish bloating after eating about 8 or so feeders my kids gave them about six days ago. Worse, the pet store said that many of their feeders died on the following Monday -- and we fed the feeders to our Oscars from the same batch the previous Friday, since they looked really frisky and healthy. I will try feeding my sick oscar with skinned peas, but have seen conflicting advice re: epsom salts. Q: will it eventually poop on its own? Oscar seems fine and quite normal tonight in terms of behaviour -- since Oscars don't get 'pregnant', I guess it's a blockage or parasite in digestive tract? Thanks for your help!! Interesting to point out, my other Oscar is just fine --- perky, hungry, curious river dog. Thanks folks, dooger

im not the expert here but ive learned some from reading all the posts, but heres my suggestion

first of all we need your water quality, whats the ammonia, nitrite and nitrate?

i think he might have some blockage, especially since he ate a bunch right before, stopped eating after, and you could see it is right before his anus. i suggest fish laxatives, if you cant find them in stores, look up online something that induces pooping in fish. pictures would be good too f your fish. it shouldnt be a parasite because there arent many parasites that would cause that big of a mood change, and bump. then again, those guppies arent the healthiest or most pristine fish in the world...

then again, this is my suggestion, by no means should you immediately do what i said, wait until a couple experts comment. it's wrong to say i know exactly whats wrong

i would check my water readings, stop feeding for a day or two, if he eating try some frozen peas, you could put epson salts in the water this helps with constipation, x

Any chance of a pic?

Your fish may be a bit constipated. Dont try to feed him for a few days and hopefully he will poop it out. It has been posted a few times where a fish has become lethargic are gorging on feeders only to do a big poop.

We do need water test results for ammoina, nitrite and nitrate