I agree with TTA's assessment, but I would add a real caution. As I said, I have experimented with crushed coral (in two different tanks), dolomite (in three) and aragonite (two tanks). I also have very soft water with basically no KH. Both GH and KH are 7-8 ppm which is less than 1 degree.
These substances all raised the pH fairly rapidly and significantly. The dolomite was used when the tank water was at or below 5, and it raised it to 6.4 to 6.8 within a couple days. This was back in the 1990's so I can't be more specific. I did not test GH/KH back then. And the tap water itself had a pH around 5. More recently, within the past five years, I experimented with aragonite and crushed coral separately. The aragonite is the better of the two because it like dolomite includes magnesium as well as calcium, whereas crushed coral is calcium. This time, I knew soda ash was being added to the tap water to give a regular pH around 7, which lowered to around 6 in the tanks I was experimenting on. Both substances sent the pH soaring within a few days (3 or maybe 4 I believe), from around 6 (possibly below) to 7.6 and 7.8. I was using about three tablespoons in the filter of the 115g tank and the 90g tank, so very little did a lot. I cut this down to 2 tablespoons after a major water change, but it didn't lower the pH. I removed the substance, and the pH returned to normal over several days with normal water changes.
TTA and I have discussed this a bit, and it is likely the very low GH/KH providing no buffering that allowed the pH to rise so fast and by so much. So I would just caution you to go very slow with very little. And I would recommend aragonite as preferable for both minerals. Plants need magnesium as well as calcium, so this will benefit more.
Byron.
These substances all raised the pH fairly rapidly and significantly. The dolomite was used when the tank water was at or below 5, and it raised it to 6.4 to 6.8 within a couple days. This was back in the 1990's so I can't be more specific. I did not test GH/KH back then. And the tap water itself had a pH around 5. More recently, within the past five years, I experimented with aragonite and crushed coral separately. The aragonite is the better of the two because it like dolomite includes magnesium as well as calcium, whereas crushed coral is calcium. This time, I knew soda ash was being added to the tap water to give a regular pH around 7, which lowered to around 6 in the tanks I was experimenting on. Both substances sent the pH soaring within a few days (3 or maybe 4 I believe), from around 6 (possibly below) to 7.6 and 7.8. I was using about three tablespoons in the filter of the 115g tank and the 90g tank, so very little did a lot. I cut this down to 2 tablespoons after a major water change, but it didn't lower the pH. I removed the substance, and the pH returned to normal over several days with normal water changes.
TTA and I have discussed this a bit, and it is likely the very low GH/KH providing no buffering that allowed the pH to rise so fast and by so much. So I would just caution you to go very slow with very little. And I would recommend aragonite as preferable for both minerals. Plants need magnesium as well as calcium, so this will benefit more.
Byron.
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