Poorly Discus

[chemflex]

I have a 180 litre tank with 3 discus in, some congo tertas, some cardinal tetras and a male siamese fighting fish. The water parameters are all absolutely spot on, but one of the discus's has gone extremely dark and has started to want to live around the heater. The fish also has a small white patch on his back, but is still feeding although not much. All of the other fish are fine.

What do you think I should do, treat with Protozin?

Chemflex

 

[WILDER]

The white patches does it look like cotton wool, or bleaching beneath the skin.
Any redness to the patch.

Darkening in colour can be a number of things from bacterial,parasites.
Any signs of flicking and rubbing.

 

[bugsy66]

Three's a crowd, take some time to sit and watch the fish. It almost sounds like it might be getting picked on, with 3 discus you will have issues for sure. Five is a nice mix as it spreads the agression around better.

If two of them have paired up then they will continue to pick on the odd man out.

If the fish are not fighting amongst themselves then its something else. But do eliminate this first before dumping chemicals into the tank.

I have Discus myself too.