Originally Posted by
DJW
Well I'm at a loss to explain what you are seeing Frank. To get water down to pH 4.5 you would have to add enough acid to burn through all the buffer until the KH is 0, and then you would have to add even more acid. I use 100% RO with KH=0 and I have to add 3 ml of muriatic acid to get 50 gallons of water that low. A biofilter could do all of that if it had enough time, but the KH would have to be 0 first.
It sounds like the discus are doing well except for something about the water that is causing a problem with large WCs. It might be that ageing is the only way to allow for larger WCs. I have these water barrels in my little fishoffice, its so crowded in here you can hardly get the door open, but I wouldn't be able to function without ageing the water.
At that stocking level you need a lot of water changes, and 5x a week is pretty good although you might need more than 30%, or maybe some crushed coral in the filter to replenish the buffer.