Salmon Catfish ....somethings Wrong!

Hi everyone.
I brought home a salmon catfish yesterday and ever since i put him in the tank it has started to break out in white patches...not spots...and the fins are starting to decay.....
Water conditions are perfect ...and no other fish are effected except the other salmon catfish i about 2 days before..
I live in Australia and the temp in the tank is 28c 84F with the heater turned off for the last 4 days..Could it be the water temp or some sort of fungus?

He is not desplaying any other symptoms,but is eating well etc

I'm betting it is columnaris. This is a bacterial infection, so you will need to treat with antibiotics. Also, this bacteria thrives in warm water, so you NEED to get the temperatue down. try freezing bottles of water and ptting them in yor tank. Also, have a fan blowing on the srufaceu will help lower the temperater. My my keyboard is acting screwy, so i'm gonna give yo links for some info.

Also, are yo aware that this fish gets 50 cm long?

http/www.flippersandfins.net/flexibacter.htm
http/www.thetropicaltank.co.uk/hdcolumn.htm

Thanks for the help ...yeah i was aware of there potential size...i have a 10ft tank

I want a ten foot tank

I just wanted to warn you on the size because i have seen some very unaware people on here with huge fish in tiny tanks.

Also, adding some salt to their water would help. I saw that they can be brakish or fresh water, so they should have no problems tollerating it. I know last summer I started tossing ice into my bettas tanks, and just gave them some extra dechlor before.

Oh and a random FYI: restarting a laptop after spilling water on it can fix the keys acting screwy and get non-functioning keys working again

Just put in some fungus medication and aeration is goin full ball.....and after 10 min already seams to be a bit more active...I have been trying the frozen bottles of water to bring the temp down for the last 3 days but it is so hot here it melts quiker than it is cooling the water....
We are supposed to get a cool change this afternoon,so hopefuly it will help

thanks for ur help