I finally broke weak and purchased an RO+DI system. I am wanting/needing a Ph of around 6-6.2--Maybe a little higher, maybe a little lower, but right now that's my mark.

I have Barr's GH Booster, so I will be using that, at least until its gone....So I need to understand what I am doing......

I am assuming that I want a KH of about 4, Correct? What about GH?--what am I looking for there?

I've read a ton of threads here and at TPT and APC, but its all kind of gotten jumbled around in my head.

What am I looking for for KH and GH with a PH of 6-6.2 without C02?

TIA

Most just blend the tap with the RO to hget the KH, then top off any GH with the booster.

Regards,
Tom Barr

I collect my RO water in a 5 gallon bucket. Since you must only use cold water with RO units (to protect the RO membrane) I usually drop a small heater in the bucket once it's full to warm the water to tank specs. I also drop in a water pump to circulate the water to speed heating and also to help with mixing the reconstituting powders.

I then add 1.5 tsp of Seachem Equilibrium to increase the GH (you would be adding Barr Booster in your case, probably different amounts also) and .5tsp of plain baking soda to increase the alkalinity (KH). I add a few drops of Seachem Prime just to be sure all chlorine/chloramine is neutralize (since I don't keep up with how long I've been using my carbon stage filters).

Last time I checked, this puts my GH around 6 and my KH around 5, or maybe the other way around. Remember, this RO water is starting out with a GH=0 and KH=0. Anyway, I works well for my plants and fish so I've never felt a need to adjust it. I dunno what my PH is because I use aquasoil and blast Co2 so my in-tank PH is always on the low side, I never test. Back when I did test seems like it was in the 6.x range is all I remember. I don't even have any test tubes left..broke them all and never replaced them. Math/observation is more trustworthy anyway.

The baking soda to increase KH is what's going to affect your PH the most. The less KH you add, the lower your PH will be (since you aren't using Co2 which lowers PH). If the aren't adding Co2, you don't need the high KH to buffer your water against a PH crash.

Thanx! I believe I am going to be mixing the RO w/ Tap--which for me is: Ph 8.2, Kh ~14-15, Gh ~17-18. So, from what I understand a 3RO:1T should give me about Kh 4-(3.75) and Gh 4.5 correct? Ph right now is unknown to me, so I'll just have to wait until I actually start mixing.

At a low Ph (~6) and a Kh of 3-4---what is my mark for Gh--(for the plants)?

TIA

I may be missing something here but how can one acheive a low pH (6 or so) with a KH of 3 or 4 without injecting CO2?

I don't know--and that's why I am here. If some one could take the time to spell it out for me or provide a good link--that would be Great!

I could probably spend an hr over at SimplyDiscus.com Re-reading, but their site has been down for a while now....The marine sites use high ph water, so that doesn't do me any good.

You need about 2 ppm of KH to get a pH of 6, with no CO2 injection. That is 2 ppm, not 2 dKH. You can check this out by using one of the pH/KH/CO2 calculators, such as on Measuring CO2 levels in a Planted Tank. Just remember that the CO2 in the tank will be around 3 ppm or less with no CO2 injection. So, you play around with entering a pH and a KH and seeing what the ppm of CO2 is. When it hits 3 you are in the right ball park.

Practically speaking, you can't get there by blending the high KH tap water you have with RO/DI water.

I agree, but how do I get around the Zero Buffer (Kh) of straight RODI water? Or even can I?

I have been using Seachem's Acid Buffer with this Hard water while deciding/waiting on this RO unit. Acid Buffer lowers pH it converts carbonate alkalinity (KH) into available CO2. So, it will steadily eat away at whatever KH I do have--I don't know that that's a Good thing. In theory I guess, I could continuely add more KH with Baking Soda or Seachem's Alkaline Buffer. Seems like I could work out some kind of receipe to reach the goal.

You'd need to mix your RO and tap in a ratio of 150:1 to get your KH to 0.1 which is that 2 ppm.

Using baking soda, Sodium Bicarbonate, adding 1 tsp (tea spoon) (6 grams) to 50 liters of H20 (13.21 gallons) increases the KH to 4.
[http://fins.actwin.com/mirror/Annex/...-hardness.txt]

You have to divide that KH of 4 by 40 to get 0.1, which means you divide the baking soda dose by 40 as well, so 1/40 of a tsp or...

That means .025 tsp (.15 grams) added to 50 liters (13.21 gallons) will give you a KH of 0.1 (2 ppm) which will put your PH at 6.0

I agree, but how do I get around the Zero Buffer (Kh) of straight RODI water? Or even can I?

Having a 0.1 Kh isn't very "safe" is it? Not from what I've learned over time.

I add Humic Acids/Tannins, so will that help bring down the Ph without adding C02?

I'm comfortable enough with a Kh of 2, but I really don't think I want to go below that, correct?