Lowing Gh Without Lowering Kh

[jesseoneill]

Howdy folks! I need your help!

I've been working very hard to bring down the hardness of the water in my tank (my tap water is practically liquid concrete), and after many water changes of pure RO water I was finally able to get my KH to 8.5, my GH to 8, and my pH to 7.9 (as of 1 week ago). I wanted to bring it down just a little more (somewhere in the 5-6 range), so this week I did 3 more pure RO water changes. I also tied my two new Anubias plants on to some pretty rocks to keep them weighted down, only to finally realize (three days later) that those pretty rocks were....

SELENITE

If you'll notice, selenite is a form of gypsum which is a calcium sulfate--in other words, not good for lowering hardness. When I tested my water today, my stats were KH of 5.5 (yes!), pH of 7.5 (I added CO2, yes!), and GH of 17!!!

My question: Is it safe to lower KH even further in my quest to bring GH back down? Should I just keep putting in pure RO water? If this isn't a good idea, how would I go about lowering GH without touching KH? I guess I could always raise KH with baking soda and bring them both back down together, but I don't want to have to do this.

Please help!

P.S. - Anyone near Madison, WI who wants to tiny chunks of selenite that will totally throw your tank out of whack, you are free to have them!

 

[jesseoneill]

Just wanted to give this a bump; hopefully someone can give me a hand.

I'm currently thinking of mixing baking soda with RO water (I'm thinking this will raise KH while lowering GH) and doing water changes with that until GH and KH are at the same level again, then straight RO water to bring them back down.

Thanks for any help you can give!

 

[thegnu]

your fish in your profile will do fine in your water but if you want to lower it again i would just continue adding small amounts of RO water for your water changes but keep an eye on the nitrate readings to make sure they don't go up in case you are not doing enough water changes

 

[Native American]

jesseoneill, I had to deal with incredibly hard water once, and my way of dealing with it was once I got the gH, kH and pH where I wanted it, I did all my water changes w/ 50:50 RO:treated tap water to keep things where they where. My tap water didn't have enough carbonate hardness to start with, so mixing with RO just made that worse...had to leave a bag of crushed shells in my canister filter, and add some Kent kH buffer to the new mix every time. In short, I wanted the new water to be close to the water I was removing.

This mixing was a pain, but it worked. Right now I live in an area where I can get by with just treated tap water, thank God.

v/r, N-A