Everyone slow down you can use melifix for Popeye it will help reduce swelling but the red in the eye could be from so many things. Parasite, worm, bacteria, fungus. if it is from a worm it's more than likely anchor worm bad if it has gotten into the eye it self. You will in any case need to feed with an antibiotic and treat in QT. It could be from fish rubbing on rocks and it is now infected. The sign of blood from a fish is always really bad sign and don’t get frightened from asking for help. But don’t just go out and buy some drugs and start putting them in your tank you always treat in a QT. Only once you know what you are dealing with so you are dosing with the right medications. Some medications can kill a fish if it is not to be given for a particular problem. It’s the same for humans if you are having troubles breathing some med’s can kill you instead of help.

The last poster just wants you to realize that at the first sign of trouble try and get some local help. To help over the internet is difficult enough especially without pictures and all of your tank parameters and by that you need to post the readings. Don’t just say everything tests perfect, to many that means 2 things (1) you didn’t test or (2) you don’t have enough test equipment to do all the tests that some people may want to see. The second is ok, we will make do with what you can give us you can have a LFS do a more comprehensive test the next day.

You will need to figure out what caused it to protect the rest of your tank if it is a parasite of some kind.

Bill