Removing calcium and magnesium?

[aquarium]

I have the swimming pool working okay with the high CH = 430ppm, but I'd like to lower it for my aquarium. (I used the aeration method to get alkalinity down, and that's a big hit.) Our water is unusual because the calcium:magnesium ratio is closer to 2:1 rather than the normal 3:1 or 4:1. I think the high magnesium is causing plant growth issues.

I adjust the water in a large trash can. Given a 35 gallon at a time working volume, is there a way to lower both calcium and especially magnesium?

[chem geek]

I adjust the water in a large trash can. Given a 35 gallon at a time working volume, is there a way to lower both calcium and especially magnesium?

I don't know of any other methods other than what was described in the earlier posts in this thread. For magnesium, I think that the water softener approach is much better than the precipitation method I suggested since precipitation is OK at removing calcium and is not as good for removing magnesium.

Richard