Thanks. It was shocking to see how many resources don’t even mention this. It really helped me. I just did a testIn my opinion, 30 to 50 is perfectly fine to use.
If you feel better about that range, that's what you should use. The main thing that we teach is the ratio of fc to cya.
As long as you maintain the ratio according to the fc/cya chart, you should good.
We have found that using a higher cya can be beneficial but I wouldn't have any issues with 40 to 50 cya.
I added a touched of acid and a bit of stablizer. I’ll raise ph if it drops a bit.