Pressurized CO2, low KH, big pH drop - what now?

[src]

I'm having trouble figuring out what to do about the CO2 and pH in my 120. I'm using a pressurized CO2 system, and trying to maintain ~30-40 ppm CO2, but this is really screwing up my pH.

My tap water measures around 7.2, with 2-3 degrees KH. I've been slowly bumping up the CO2, but to get to 30-40 ppm, the pH drops drastically. It has even hit 6.0, and that's lower than I think I want to go.

I have some crushed coral, and would like to add it to the filter to raise the KH, but I keep reading that the additional buffers screw up the CO2 calculations, so I won't know how much CO2 is actually in the water.

What's the best way to handle this situation? Should I just add the crushed coral and "wing it" on the CO2, trying to keep the bubble count in the vicinity of the current rate?

Current tank inhabitants include tetras (Pristella, Rosey), Rasbora Hets, Delphax Corry cats, some Angelfish, Ottos and a Bristlenose. Any advice is welcome!

 

[rich311k]

Actually raising your KH will not mess up your CO2 calcs. It is only if you have a buffer besides KH that messes up the calculations so adding some CC will not effect you at all.

 

[src]

Thanks! CC it is then.

 

[Lonewolfblue]

You will be fine adding the CC. Just a small handful is all you need. And remember it will take a couple weeks before you start noticing any changes. When I had CC in my 75G, my kh went from 60 to 100 in 2.5 weeks, and that's with regular 50% PWC's weekly.

 

[Zezmo]

If your Ph is swinging, it suggests the CO2 is unstable since that is what is most likely acting on your Ph.
Are you are getting 2Kh or 3 Kh, which is it, accuracy is more important at those low ranges to get accurate CO2 calcs.

If you have 3dKh, and starting Ph of 7.2, 36ppm of CO2 should get you at 6.4ph. These are all good ranges to be in for most normal fish.

IMO, stabilize your CO2, and practice getting more consistant results from your tests. If you test the same glass of water 5 times in a row, you should get the same results. Without getting into why home tests lose accuracy due to user variation (reproducability). I will say that you have to be somewhat careful, and control the test conditions a bit to get stable and accurate measurments from home test kits.

If you get wacky results from a test kit..... try another test kit.

 

[src]

Sometimes I get 2 dKH, sometimes I get 3 dKH - not on consecutive tests, on different days. Also sometimes it's a marginal change at 3, sometimes solid. The water supply isn't as stable as we would like.

Testing methodology isn't in question here, source materials are.

As I said, I was working my way up to 30-40 ppm. I knew quickly that I had overshot when the pH went to 6. The problem is that the difference between 20 and 60 ppm is a VERY touchy adjustment on the needle valve of my CO2 regulator. Getting 1 bubble/s is easy. Getting 3-4 bubble/s is easy. In between is HARD. My next regulator won't be the AquariumPlants version.

 

[m-man]

can someone send me some CC for a few dollers, all they have in the stores around me are , at the smallest 10lb bags, which is way too much, also too expensive, i just need like 1lb for the same reason, raising Kh,

 

[src]

Ask them for some from an open bag - most stores that have saltwater tanks will have an open bag in the back somewhere. I bought a pound for about $0.70 from my LFS.

 

[m-man]

..oh yeah, never though of that, ill try that