question of general interest - discus turning dark

[Miamiheat]

Hi,
I gave been reading dozens of threads on SD forums in the past few months. But for the life of me i still can't figure out the following:

One of your discus starts being very shy and one day it turns very dark.

At this stage i think I am right in saying the first thing to do is test your water. If issue is as obvious as amonia or nitrites i consider this "easy to solve".
But what if your parameters are fine?

I want to know exactly what to do if my fish turns dark assuming that i covered the steps mentioned above. Do i separate the fish from others and is there a common procedure to follow?

thanks

[pcsb23]

I've moved it to the discussion area as it is not about a specific case.

Ideally you would spot issues before they turn dark. But if you don't you need to do some detective work. Water is always the first thing to check, after that make sure that temps and everything else in the tank is fine. Then work out what has changed - may be new fish, plants, food etc ... maybe there is pairing activity or other fish causing issues. It may be aggression from other discus.

Most disease can be traced back to some stressor or event. Stress can take time to develop to the point where fish get sick, most people just don't accept this, even though it is true. The vast majority of illness in discus can be traced back to husbandry issues.

[Miamiheat]

Thanks Paul. I have seen fish turn dark one day and die overnight. I have seen them last a long time as well. Now when I have a tank loaded with "healthy" Discus and I use the quotes because they are simply behaving like happy hungry fish. If i can figure an easy answer such as Amonia then I know what to do. But if it's more complex and I need to do more investigating do I separate the fish or do I risk leaving it with the others?