Originally Posted by Hypancistrus
Dare I suggest an aquarium product
Kent Botanica GH+ contains only calcium and magnesium. What I like about it is it's a liquid (no pre mixing or dissolving, although it needs shaked
), it's already blended, it doesn't cloud the water after you add it, and it contains no potassium (only calcium and magnesium)... although to some that may not be a benefit. To me it is, because I dose K seperately.
I used to use Kent's GH+ solution, too. I stopped because it's like 4 orders of magnitude cheaper to mix up one's own. This I have done since switching to the Greg Watson dry chemicals. Further, the stuff does not recite the relative abundance of Mg and Ca so it leaves you guessing if it's important for you to maintain a given [Mg(2+)] for your plants.
Like one of the earlier posters, I'm in a very soft water situation. Out of the tap my GH (and KH for that matter) are both at or under 1. New York City tapwater, yesss! Until recently, I'd been maintaining GH of about 3, but my swords were very wrinkly and I've decided to try upping the Ca.
I've been dosing magnesium to 10 ppm, and then making up the balance of my GH with CaCl2. Maintaining a GH of 3, this means Ca could be in short supply, so I'm upping my overall GH while maintaining Mg constant.
NOTE: GH UNITS, & TESTING.
1 dGH is ~17.9 ppm CaCO3, ~ 7.14 ppm Ca(2+).
Atomic wt. of Ca = 40
7.14 mg/l = (7.14/40)mol/liter = .179 molar.
That is, a solution which is 0.179M in Ca(2+) will test out at 1 dGH.
And since the test kits react the same with Ca(2+) as Mg(2+), it is also true that a solution which is 0.179M in Mg(2+) will test out at 1 dGH. Note, this is MOLES per liter, not GRAMS per liter. It makes a difference; be sure you understand why.
Figuring how to dose Ca and Mg to the required molarities is trivial and is left as an exercise for the reader.
Don't mess with seashells, coral, etc. hoping to get KH and GH right. For one thing, you don't know the Ca/Mg ratio in seashells or coral. It may well be that there's only vanishingly small Mg available, or it could be quite the reverse (and I imagine it differs between species of shells/coral). Coral dissolves sloooowly, and CaCl2 and MgSO4 dissolve instantly.
As for KH it's trivial to obtain baking soda and use it to modulate your KH as needed. Even here in NYC a box of the stuff is cheap, like 85 cents, and should last a very, very long time.