Generally speaking, I read that if gh levels are 3 or higher, then there should be adequate Mg and Ca available. Is this true ? How likely is it that there might be a shortage of either element even if the gh levels were at what would be considered adequate ?

In a low light tank with say 1.5 to 2.0 wpg what would be the suggested co2 level ? Is it still 30 ppm or is something less ok ?

As I write this, I just got back from the LFS and sold my first cuttings from this morning's pruning session. Less that a year ago, I wasn't sure I would even be able to grow plants, never mind sell what I grew.


Henry

You need both Mg/Ca, not just a general GH.

You can likely get away with less, say 20-25ppm of CO2 in lower light tanks.

Regards,
Tom Barr

It is my understanding that gh is comprilsed primarily of ions of Mg and Ca. What I'm wondering is could there be an imbalance where most of the gh was due to either Ca or Mg and one or the other might be in short supply. Most people I think if they have a gh reading of say 6 that both nutrients are available in adequate amouts.