What is a "good" Ca/Mg level?

RoseHawke said:

Calcium - 11.7 mg/L
Magnesium - 4.10 mg/L

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Hi,

That is good level.
The problem is plants will take it fast. You will need to replenish by doing a water change or by dosing it.

Edward

Thanks. I'm doing 50% (approximately) weekly water changes. Enough?

Cindy

Plenty.
I'd just do the the water change, it's simple.
I'd not ajust a KH of 2, I'd just leave it and add enough CO2 to get 25-30ppm.

The East bay tap like this.

Regards,
Tom Barr

Thanks, Tom. I like "do nothing" (just do water changes,) as advice :-D. Life is complex enough. That's awfully basic though, not raising the KH. That would be about 6.3? Our local tap water is over 8.0 out of the tap, about 7.6 or so (if I remember correctly, it's early and I don't want to bother checking my records :-s ) after it's "rested." Trying to keep some sort of moderate average for the fishies. Right now I've got the controller set to keep the ph at 6.6-6.7. Kh of 4-4.5 means 25-30 ppm. That's really a bit lower than I want, but I didn't want to raise the KH any more. Unfortunately I can't totally depend on a KH of 2. At times it'll be lower (Ca/Mg as low as 12.4/3.2 TH of 51 according to water authority.)

Well then, you better check and keep an eye on the KH when you determine your CO2 levels, not a bad idea anyway. Dose the GH though.

The CO2 uptake and dosing will be the same even if the KH moves around some. As long as the bubble rate is stable, so will be the CO2 available to the plants.

Regards,
Tom Barr

Thank you for your reply, Tom. I am trying to keep an eye on the KH, at the moment testing and adjusting with each water change, and a couple of times a week just to "make sure" it's where it needs to be.

Pardon my ignorance, I'm not sure I understand your use of the phrase "dose the GH." I'm a bit confused (a normal state of affairs at times :-s ) as to what exactly you mean by this as this is the first time I've run across this specific phrase. Clarification, please?

I'm also interested in this topic.

If my tank eats about 20-30 ppm NO3 each week, how much Ca is used and have to be dosed to remain at the start level (in my case 15-20 ppm Ca from tap)?

I am also interrested in this topic. I also wonder if one could measure a decrease in GH over a period of time as the plants use up Ca or if the it is still there, but in another form no longer available to plants?