Help with sick fish

[eeneryllek]

I added 2 oscars to my established tank on Sunday. Don't have a qt tank, so let them sit in the tank in the bag about 45 min then added about a cup of water to their bag every half hour for several hours. Added only the fish, no bag water to the tank. They were doing great until I got home yesterday evening. They both have white areas all over and their fins are looking ratty. Was thinking ich at first, but looks more like peeling than salt like spots. It's possible that the knife is beating on them and that they're running into the rocks. Does this look like battle wounds to you?

Any ideas what it is? And how to treat?

75 gal tank
Fluval 405
0 ammonia, 0 nitrite
Nitrates are around 5-10
Last water change was Saturday
Tank has the 2 new oscars, 1 pleco, 1 pictus cat, 1 Asian knife

Thanks for the help!

 

[jlk]

Welcome to AA!!

Unfortunately, this is going to a lesson learned the hard way. The oscars appear to have a serious bacterial infection (either columnaris or aeronomas) and it will need to be addressed as a tank treatment due to everyone else being exposed.

Start by lowering the temperature gradually into the low 70's or high 60's. This will help slow bacterial multiplication. Gradually increase the salinity to .05 to .1%. Treat daily for atleast ten days with a gram negative antibiotic and daily water changes.

Quarantine tanks, especially when working with a large tank, are worth the effort. They do not need to be expensive- a 20 or 40g Rubbermaid type tub (under $20), a cheap filter and a heater (if needed). Please ask any questions!