Oscar Fish Looking Bad After Adding Plec

[ReMz]

Appologies if this post is blunt. I have to run and cannot post anymore at this time. Will be back in 4ish hours to provide more info. Just looking for the best advice I can get with the provided info right now.

Tank size: 75 Gallon
pH: ~6.6 (really acidic for some reason)
ammonia: <.5 (slight spike after adding plec)
nitrite:0
nitrate:0
tank temp: 78F

Tank Mates:
Blood Parrot + Just deceased Royal Pleco

I added the Royal Pleco on Sunday and noticed he might have had a bit of what appeared to be a rupture on his back. I didn't get a look and he has been in hiding since this morning when he was upside down in the middle of the tank.

Fish Symptoms:
Royal Plec found dead this morning.

The Oscar has been in the tank a little over a week and has been acting very sulky on and off. He had perked up quite a bit before Monday. He is acting very lethargic, laying sideways, and I have seen him "slap" the bottom of the tank once or twice in 48 hours. He looks to have a bit of a white coating forming on his side.... but with his location it is hard to tell.

I've done a 30% water change and added Maracyn 1 & 2.

Volume and Frequency of water changes:

Been doing 10% every day or every other day. Tank has been established for 1.5 weeks with mature filter media.

EDIT (Pics):

 

[minxfishy]

That doesnt sound good and Im not really sure what to advice, other than keep up the treatment. Let us know how you get on, keeping fingers crossed for ya.

 

[ReMz]

Ok update. I've moved the Oscar into a fully cycled 5gal tank for quarantine and treatment. The Maracyn I dumped into the 75gal was just a quick "something" as I was running out the door. There is still activated carbon in the tank so it was probably useless.

I wish I had a little larger quarantine tank, but this will have to do. I've just started him on his first dose of Tetracycline and a bit of aquarium salt (seems internal and external bacterial infection to me). He has kind of a white, slimey coat that had formed this morning on his side, and his poop was white and stringy. He will not eat.

Anything else I can do at this point? Any input or help would be greatly appreciated!

 

[LauraFrog]

A photo would help - I've had so much trouble with foul columnaris that I will recognise it. Rupture on the back of the plec does sound a bit like it. Some strains are tetracycline resistant. As far as I know maracyn if used both 1 and 2 is effective on all but the worst strain. if the oscar had that it would already be lying on its side gasping.

 

[ReMz]

Just managed to catch him out of hiding. Here are some pics

 

[ReMz]

Bump

Now treating for ich as well (can be seen in the pics actually).

Any advice other than what I'm doing