Do these dosing calculations sound about correct?

[Ocean’s Piece]

measuring cups. I just had to mix up a new batch tonight.

But like I don't know my exact gallons of water in my tank. I estimate it to be around 200g in water volume, but I have no clue if that is accurate. And as I mentioned, my usage is constantly changing. In the past year my usage has doubled. Calculators got me close, but I had to dial it in manually.

I keep my alk between 8-8.5. The increases in usage/drops aren't drastic, so it's not hard to keep up with weekly/bi-weekly testing. At worse it'll rise up slowly, but then it'll start to use it up. Sometimes I'll just do a little manual dump if my usage is even but I want to raise it up a point or 2.

I also don't do water changes, so I don't have to worry about that changing my values.

Just out of curiosity since I see you said you do no water changes, how much magnesium do you dose and how often? The test kits for magnesium are all terrible from what I have done and seen from others and I’m unsure how I would go about adding it. I’ve heard like 1/10th of the calcium and other things, but what’s your way?