You edited your post.
I was going to scold you about testing monthly (that's not enough). One week to 2 weeks is a perfect schedule though.
In the interest of full disclosure though, there are times I'll let testing slip and it becomes a monthly thing. But, 50% of the time, it's been regrettable. I was always able to guess by observation when Ca and Alk were slipping, but it's taken a while to figure out the tells of a Mg slip and so those other 50% times were times I usually found my Mg had totally crashed. Nowadays though I can even tell when Mg is slipping (the anemones in particular are surprisingly quick to respond to Mg). So I'm sort of falling back into two weeks but the "do as I suggest, not as I do" part of me still wants to suggest weekly for testing. If you think of me as a hypocrite, look at my tanks RIGHT NOW and then tell me if me telling you not to do as I do is a bad thing (I have no idea if that last sentence makes any sense. I just reread it and it makes my head swim. I'm going to let it stand, though.)