It is important to have some calcium and some magnesium, enough of both that it meets the plant's needs. Unless someone has some data to show what the "best" levels are, I don't think it matters what our opinions are. Also, to the best of my knowledge, it doesn't matter what the ratio is, just that there is enough of each. If there isn't enough, then adding some more should give you noticeable changes in the plants. So, if you want to try to figure out what is best with your tank and plants, just add some of one of them, calcium for example, then watch the plants for a week or so to see if you can pick up any improvements. If you can, add a bit more, and repeat until you don't see an improvement. That will be the "best" level. Then repeat with magnesium. You could probably start with magnesium and get the same results. I'm betting you may see some effect of adding some more magnesium, but probably won't from adding some calcium.
Then, there is manganese. I understand that it has value too, and may be in short supply. So, you could do the same testing with manganese.
Last edited by Hoppy; 07-30-2012 at 04:34 AM.
Reason: Another thought