I have had several oscars over the years,and as you can imagine I have lost them in wierd ways but those are usually due to my childern trying to help take care of them.Fifteen months ago, I bought a red oscar got it home,put it in tank and everything was fine.About 11 months ago I moved and it caught an infection that after it was treated it went blind,no biggie I switched to a 90% live food diet.The other night I watched it as it stalked and ate its evening snack,it was moving fine and had no problem eating the comet.The next morning I went to talk to it and found it on its side not moving,I thought it was playing possum(its favorite game),so I touched it with the net it was dead.I removed it from the tank and noticed a very heavy slime coat on it.The slime was thicker and heavier than anything I had ever seen even on a channel catfish,the back of its throat was black,its gills looked ok.Does anyone out there have any ideas as to what killed "fishous"?I would be grateful for any help,I have 2 small ones that I would like to put in that tank.

The comets killed your oscar. Comet goldfish have a chemical in them called Thiaminase, which breaks down Thiamine (Vitamin B1), which leads to a nutrient deficiency. A black throat is the #1 sign.

Next time, don't ever feed comets.

artemis1 wrote:

i concur with art on this. sometimes, ever the guppy
could cause death to oscar when you are not sure of their
origin. that is wgy most member here discourage feeders.