PeteLockwood;3702400; said:The advice that you don't need to do water changes until the Nitrate hits 40 can be tossed in the garbage can - water changes are for more than just reducing Nitrate. Since you already did 50% and the fish survived it, I'd do another 50% - hopefully that'll add enough Kh to get things stable and work out how to maintain the Kh going forward.
I advised this because he had just done a 50% water change the day before. Doing 50% water changes every day can also stress out fish if they're not used to such a thing.
If all the parameters are in check, with only his ph at 6 and if that is staying consistent, what is the point of doing 50% water changes every day?
I was suggesting to watch his nitrates. If they jumped back up, then do a water change. Basically, I was suggesting since he had done one the day before, to take a day off and monitor the tank. Watch the fishes activities and check the parameters. If anything was off, then do a water change immediately. If things were fine yesterday, then do a water change today. Then spend tomorrow monitoring the tank again. Then the next day, do a water change. At some point, the parameters should start leveling off and the tank should be good.