I have Discuss fish in my tank. I added timber logs to soften the water but there is a yellow water stain. The logs have been in the tank for a few months yet despite the numerous water changes and the yellow stain remover (sachet that one places into the filter)the yellow reappears almost instantly! The tank looks dirty all the time and is very aethetically unpleasing! Must I have these water logs for discuss to thrive? Someone told me to place the logs in chlorine for about 20 min then wash off and allow to dry in the sun so that the yellow colour is bleached from the timber? Im worried that the residue of chlorine will kill the fish? What do I do?

Discus are like angels and tetras, from the Amazon region. They require soft water on the acidic side, like that of their natural habitat. This can be done by adding peat to your filter and placing wood in the aquarium. The down side it darkens the color of the water. The aesthetics may not seem pleasing to you, however, the fish are benefiting. It's your choice, take it out to please yourself or give the fish a healthy environment.

Discus, despite their vivid colors, love murky waters, so as GZDZ said the fish are loving it, although it's not very pleasing to look at.

If you have a filter with carbon it should take care of the color over time.
You can also remove the wood and boil and drain it several times before putting it back in to help remove the color.

We had discus for years and never had wood in the tank, they were in just a regular tropical aquarium with other fish, they were obviously happy because they bred several times a year.