Re: NANFA-L-- pH, Hardness, Gravel

Jerry Baker (nanfa at
Thu, 01 Sep 2005 09:08:57 -0700

Gerald Pottern wrote:
> Steve - i usually put a teaspoon to a few tablespoons of African Cichlid Gravel (= crushed coral, aragonite) mixed with inert gravel (lava rock, quartzite, etc) in a small box filter to add just a little hardness & buffering in my soft water tanks. Raleigh/wake forest tap water is very soft & buffering is used up quickly. dose used depends on fish load & pH/hardness preferences -- even for blackwater fish i use a little bit (after tank has cycled and ph starts falling), otherwise pH will plunge below 5, and i'm guessing fish & plants get starved for Ca & Mg. Keeping it in a filter ensures water circulation to slowly dissolve it, and its easy to add/remove if pH is going too high or low. And like you, i dont like pale colored gravel for a substrate.
> Regarding Laura & Bruce's discussion, Epsom salt will add Mg but no Ca. I imagine the Ca/Mg ratio in water may be very important, as it is in land animal diets. Most aquarium hardness test kits measure Mg+Ca combined, and wont tell you if the ratio is out of whack. Aquaculture & environmental testing supply companies sell fancier kits that can measure Ca and Mg hardness separately, or your local water dept may provide data. HAs anybody got info on what's a GOOD Ca/Mg ratio for: a) blackwater fishes, b) soft neutral water fishes, c) hardwater fishes, d) freshwater shrimp/crayfish ?? (and Na/K too, while youre at it !) The ion content of native waters is NOT always indicative of what's best for animals in captivity. -- gerald, hangin on the neuse

I do not know of any research outlining the Ca/Mg ratio requirements of
various aquarium fishes, but I know that those elements generally occur
in a 2:1 ratio. That's also how I mixed CaCO3 and MgCO3 (2:1) when
adding hardness to my soft water planted tank. You can get pure CaCO3
and MgCO3 at a health food store. People take them as a supplement.
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