Just my opinion, because I use RO water. But I wouldn't "subtract" the .4 of your plain water. Look at the overall number, which is still 2.0 and high imho.
Generally speaking, I'm pretty sure (just opinion again because I use ro water) you can go very light on cal-mag if you're adding any at all since that's what will be in the tap water.
When I want to take regular light pics, I bring in 1-2 cfl's and take them right at lights off or right before lights on.
Generally speaking, I'm pretty sure (just opinion again because I use ro water) you can go very light on cal-mag if you're adding any at all since that's what will be in the tap water.
When I want to take regular light pics, I bring in 1-2 cfl's and take them right at lights off or right before lights on.