zdam20

I need to raise my alk a little so I can hit the 30 ppm of CO2 and still keep a resonable ph. I purchased some CaCO3 powder at a local health food store and I've got a couple of questions. How many grams of powder do I dissolve in how much water? Once that's answered, how much do I dose of the liquid? For example, my tank is 150 gallons and my kh=1.75. I'd like to raise the kh to 4.2-4.5. Any help would be appreciated.

Nevermore

Hi zdam20,

This site should give you the info you need: http://www.rexgrigg.com/waterchem.htm

Basically, to raise the KH with Calcium carbonate, you will add 69 grams to your 150 gallon tank. That will raise the KH (as well as the GH) by 2.75 degrees.

I would question why you think you need to raise the KH. I think your thinking might be wrong; it sounds like your using the CO2-KH-pH chart to come to the conclusion that you need to add KH and that is wrong. You can't change KH or pH to adjust your CO2 level. Also, see this: http://www.aquaticplantcentral.com/f...-amazonia.html

zdam20

Thanks for the reply Nevermore. What I am doing is controlling the ph with a controller hooked to a solenoid on the CO2. So as I add kh the ph in the tank will go up and the controller will open the CO2 to the reactor to bring the ph down. I'm actually using 100% RO water so the only buffers in the tank will be what I add back in. Don't know if I'll have to add calcium to keep that at 20 ppm for my crs. I'll have to test for that weekly and see. Thanks again for the response.

ray-the-pilot

CaCO3 will increase KH and GH but it is practically insoluble in water. You will only get a chalky gunk adding it to your tank. The CO2 in your water will eventually dissolve the mess but it will linger some time in your substrate causing erratic results in your CO2 levels. Also, adding CaCO3 doesn’t address the need for Mg+2 another element in high GH water.

Actually, I recommend using a commercial RO water reconstituting formula or adding some of your tap water back into your RO water to get the right GH/KH.

BTW If you do have a low GH/KH tank, I recommend keeping CO2 levels below 20 ppm. At this level you will still have rapid plant growth and pearling of all your plants.

BTW2 Since you are using RO water, the pH/KH/CO2 relationship will work perfectly for you.

BryceM

CaCO3 can be used but as Ray pointed out, you really need to use a fine talc-like power to get it to dissolve in a reasonable amount of time. Those people who do use it usually dose in the evening so it doesn't cloud up their tank during the day.

Most people who are looking to raise KH do it with NaHCO3 (baking soda) which is readily soluble in water. The sodium half of the molecule isn't exactly desirable, but at the concentrations we use, it isn't that big of a deal.

zdam20

Thanks for the responses. I'm unsure of what mg+2 is. Is that magnesium? Will the pps solution using MGSO4 add this in?

nfrank

A better way to provide GH and KH is pulverized Dolomitic Lime, packaged for lawn and agricutural use. It is very inexpensive. Put a Tbs or so in a plastic bottle and shake it up to make a nice suspension. Some of the coarser particles will remain in the bottom. Pour the milky liquid into the tank and it will clear/dissolve in a few hours, faster with CO2 injection. Do it at night and you may not even notice it. Check the fert tables for correct dosing. Using an amount similar to the CaCO3 should be fine.

The dolomite is composed of CaCO3 and MgCO3 ... and the Ca:Mg ratio for GH is the perfect 3:1 ratio.

BTW, i no longer use it and as the previous folks indicated, it is not important to worry about low KH. I wouldnt want it to be zero however. Frequent water changes with my KH=1-2 tap water is sufficient to keep my levels OK. I now focus on maintaining Ca and Mg levels. I use Plaster of paris (CaSO4) and epsom salt (hydrated MgSO4) ... in equal parts by volume--which i dump in the sump, so the slow dissolving white sludge is not a problem. Without a sump, making a suspension as with the lime would help it dissolve. I add 1/2t of each with a 200L water change.