# PH swings and KH issues with auto C02 system?



## blsteve (Feb 2, 2006)

Hi, I have a 80 gallon planted tank and just converted to RO water two weeks ago.I also added a Milwalkee automatic C02 system yesterday. I have done several 1/3 water changes since changing to RO and have got my KH down to about 9 from the 17 it was before. I would guess that the KH will go down to zero after several more water changes. When I hooked up the C02 yesterday I had a PH of 7.5 and it was down to 7.1 by the time the lights and C02 turned off. When I woke up this morning is was up to 7.8! and now tonight after the lights and C02 have been on for approx 8 hours it's back down to 7.3, KH is still at 9. I went to LFS and they sold me Kent Botanica KH plus and said it would buffer the PH? My question is, do I really want to raise my KH with this stuff? What do I set the PH at and what do I want my KH to be? Are the PH fluctuations normal and will it kill my fish? I have a copy of Chucks planted aquarium calculator and kind of understand the affects one has on the other, but there must be a target PH and KH right? I can reach C02 level of 30ppm by bringing my PH down to 7 with KH of 9 or I can bring my KH down to 4 and my PH down to 6.6 and reach the same C02 ppm target. I could also add some of the Kent Botanica KH plus they sold me and bring the KH up to 14 and hit the same C02 target with a PH of 7.1, but then I am raising my KH again! I thought I went to RO water in order to lower KH and thus reduce allege.
Any help would be much appreciated.


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## Overfloater (Apr 2, 2004)

You have many questions and a few bad answers to go on. This can be very frustrating. Start with the basics. 

It is going to take alot of WC's to reduce your kH very low. I think 9 is an appropriate level and you should be able to grow most plants. 

Having a high(er) kH will not cause algae.

I find it is better to use a pH controller when suing water that has a higher kH level such as 9. Otherwise the pH has a tendency to bounce up overnight. 

Do not use any buffer, such as the Kent product to alter your water. It will cause you nothing but headaches.

Dilute your tap with RO (as you ahve already done) to produce a kH of 9 and then set your controller to keep your pH at 6.8.

This is a good starting point.


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