Right here goes Planted tank containing 4 adult Discus now ... Ph 6.8 kh 3 and GH 6.. using Ro water ... due to the fact that plants take up o2 at night I turn the CO2 off at night now I have tested the water each morning whilst the lights are off and the PH is 6.8 constant havnet checked the Ph with the lights on but my fish are a bit stressed and I was wondering if there would be a massive ph diff between lights on and off ... oh yeah by the way my KH is down to 2 but I think I know what that is as I put a small amount of pure RO water in the tank ,,, according to chucks caluculator for PPM im way under the avergae at only 9ppm but the bubbles are coming from the reactor at more than 2 per second ..... at this rate the bubbles will be constant ....

any advice as always welcome ...

It could also be a lack of o2 over the evening.

a kh under 3 can cause ph shifts and stress you're fish as well as throw off you're co2.add some bakeing soda a little at a time to raise you're kh to 3 minimum.you do add trace to you're rr/o water do you?

Yea your KH is too low. Try getting it around 5ppm's and this will give you a more stable pH. I have mine set a 5ppm's and add CO2 on a 24/7 basis. IOW don't turn it off at night. The pH swing will only be marginal and will not give any problems. Well it should not give any problems. It really depends on your own specific water conditions.

BTW I do use only RO water and add my micro/macro and all the other stuff every time I make a 25 % water change which is weekly.

Well after having checked my Ph of the water this morning after a full 11 hrs of lights on the Ph is still 6.8 so it isnt the Co2 or Ph looks like it might be something else ..

Thanks for the input

aquaphish,

Don't you mean 5 degrees? 5 ppm of kH is VERY low!

Yeah me thinks he means 5 degrees or 5x33ppm 168 ppm

I thought it was each degree was ~17 ppm?

Rex you're correct, 17.9 ppm = 1 degree kh to be exact.

Marcel

ohps me thinking of conductivity sorry :shock: