5 Year Member
Soft-water fish must have super-efficient ion-uptake cells in their gills (and intestines?) to get all the Ca and Mg they need from an environment that hardly has any. Since we usually measure total hardness without distinguishing Ca from Mg, I'm wondering whether there's some acceptable range of Ca:Mg ratio they need. Seems like this would be even more critical for soft-water fish than for hard-water fish, where both ions are usually in abundance. Anybody got info on Ca:Mg ratios in natural soft-waters, e.g. S.Amer, W.Africa, SE.Asia ?? I normally use tiny amounts of crushed coral/aragonite gravel in a filter to provide (presumably) both Ca + Mg and weak buffering for soft-water fish after the pH starts to drop (my tap water is about 2 dGH). Just wondering whether Ca/Mg imbalance might be one of the problems folks have with "delicate" species.