High pH with moderate/Low GH and KH...How can I raise GH and or KH? - Tropical Fish Keeping - Aquarium fish care and resources
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post #1 of 2 Old 12-28-2012, 12:50 PM Thread Starter
High pH with moderate/Low GH and KH...How can I raise GH and or KH?

...I'm in the process of running a fishless cycle for an African Cichlid 55 gal. tank. My substrate connsists of a mixture of 15 lbs of CaribSea® Aragamax Select Aragonite (From Petsmart) with about 25 lbs of Pool Filter Sand. (mixed throughly with one another before adding to tank) Tank has been set up for 11 days now and the pH is holding between 8.1-8.3 (Very hard to decipher colors in the tube and chart with the API Fresh water Master Kit.

My GH has gone up from (Tap water - 5.0 degrees (drops)) to GH of 9 degrees. But for african Cichlids I'd like it to be higher at least in the 12-15 degree range

My KH in tap water was 4 degrees, and 2 days after tank was set up was at 7 degrees, but yesterday was down to 5 degrees.

My substrate is about 2 to 2.5 inches deep through out the tank, would I be better off adding some more Arganite, another 5 lbs maybe? Even though I dont really want a much deeper sandbed.

I also have crushed coral which Ipurchased but hve yet to use in the filter (Fluval 406) in one of the sections. I have not done this yet, hoping I could get away with the substrate providing enough minerals to raise the hardness. Will this help raise the Hardness? without raising the pH?

Alternatively I could add baking soda maybe? what do you guys suggest?

One side question....which of the hardness test..GH or KH is more important when seeking to raise the water's hardness for hard water fish such as African Cichlids? Fish profiles often tell what the waterhardness preferences are but dont state if thats GH or KH? Should I be concerned with boosting GH or KH? Thanks!!
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post #2 of 2 Old 12-28-2012, 06:43 PM
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This will repeat what I set out in my PM, but it should be here for others to see and comment.

GH is the important thing as this is the measure of hard minerals in the water. KH or Alkalinity has no effect whatever on fish, plants or bacteria; it does however "buffer" the pH depending upon the degree of KH and other factors. But the GH is the issue, even moreso than pH.

You're probably in good shape at 9 dGH. The GH is Lake Malawi is between 6 and 10 dGH, that of Tanganyika is 10-12 dGH. Your pH is fine.

You could add more aragonite, but this is not likely to do much. I found that calcareous minerals increased the GH fairly slowly in small quantities such as in the filter, but drove the pH up much higher. Adding more aragonite to the substrate would be better.

I would not mess with the KH. The aragonite will buffer the pH and this is likely to be stable. Adding baking soda is not a long-term solution anyway, since it cannot buffer adequately in the face of increasing organics. And there is a detrimental side effect, namely the increasing sodium, which is not good for any freshwater fish.


Byron Hosking, BMus, MA
Vancouver, BC, Canada

The aquarist is one who must learn the ways of the biologist, the chemist, and the veterinarian. [unknown source]

Something we all need to remember: The fish you've acquired was quite happy not being owned by you, minding its own business. If you’re going to take it under your wing then you’re responsible for it. Every aspect of its life is under your control, from water quality and temperature to swimming space. [Nathan Hill in PFK]

Last edited by Byron; 12-28-2012 at 06:46 PM.
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