Africans and Hardness

brendanh

Fishmaster Flash
I'm prepping my tank to receive some African Cichlids within the next few weeks. I've got crushed coral as substrate, and it's buffering the pH nicely at 8.2. The general hardness GH is about 200 ppm, a little soft I understand for Africans.

Question 1: What is the buffering agent in crushed coral? Is it possible to leech your substrate of buffering ability through water changes, requiring its eventual replacement?

Question 2: Any suggestions for raising the GH safely for Africans? Is it actually necessary to go about 200ppm?

Thanks!
 
Paul Loiselle has published figures for Lake Malawi of 6-10 dH and pH 7.7-8.6, for Lake Tanganyika he gives 10-12 dH and pH 7.3-8.0.

I don't consider 200 ppm (~11 GH) too soft - sounds fine to me.

Calcium and magnesium carbonates will be added to the water from most crushed corals, primarily the Ca++ forms. Some of the material does dissolve with time, but the amount/percentage lost is small. Biofilm coating the grains are more likely to block solution if only small amounts of crushed coral or aragonite are used, but should be no issue when the whole substrate is available.

HTH
 
I was warned about the loss of substrate and asked the owner of my lfs about it. His answer-his african tanks have been set up for ten years. He has noticed no visible loss of substrate.
 
The key word is likely to be "noticed" there. But the other key words would be the GH/KH of the water used to maintain the tank. The KH in my mbuna tank read about 2-3 degrees higher than my tap, and I actually had very little substrate in the tank, so that in the just over 15 years it ran, I had to add small amounts twice - but it was total less than 1/2" of substrate. When I lost some, it was obvious. The tank was also pretty heavily stocked for me, so would use more KH than most of my setups.
 
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