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I am relatively new at this chemistry thing but I have an interest in this Ca/Mg relationship. According to my calculations, I need to be adding about 2.5 teaspoons of Epson salts to my 30 gallon tank each water change to get a 4:1 relationship of Ca to Mg.

Hopefully, my calculations are screwed up as that seems to be alot. Anyway, here's how I came to that conclusion. According to my city water company, I have 40 ppm of Ca in my tap water and my GH tests at 100ppm with 2 different testing kits. I downloaded a MgGH calculator program by Stuart Keeler and after plugging in that bit of info, it calculates I have 0 Mg in my tap water (which I believe according to the symptoms my plants are showing - old leaves have yellow/brown spots which develop to pinholes). According to the fertilator, I need to add 2.5 tsp of Epson salts to get about 10ppm of Mg to meet the 4:1 ratio.

I guess I have 2 questions. Is that correct, that I need to add that much? And if so, should I do it all at once or break it up over multiple days?

I am dosing EI, pressurized CO2 at 40ppm (KH of 4, Ph of 6.5), 4.5WPG for 6 Hours, 2.5WPG for 4 hours (2 lights, 2 timers), medium fish load, medium to heavily planted with Bacopa C., Rotala Rotundafolia, Hygrophila Difformis, E. Tenellus, Ludwigia Repens, Java Fern, Altenethera Reneicki.


Mike Herod
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