Cycling- test daily
Nitrate, nitrite, ammonia
Post cycling ( no more ammonia/nitrite)- test weekly
Nitrate, phosphates, alk
Post cycle ready for livestock- test weekly
Alk, nitrate, phosphates, pH (fish only)
Calcium and Mag along with above if coral
At this stage I would test the new water as well. Make sure levels are equal before doing water change. Don’t want to get a bad batch of salt and sump in 16 dkh. F*c Salinity *cough cough*. I think at this point, I rather use cheap ass instant ocean and dose my containers than rely on what’s on the box.
I would think ALK is the single most important to test for if you could only do one. Any other parameters could piss off and discolored livestock. ALK swings would kill overnight.
Everything nowadays is automated. So it’s less of a hassle. But I do calibrate and back up my trident and NP with my Focustronic. I always have Hanna/Salifret to test with monthly to make sure of accuracy. And everything gets calibrated everything every time I go through the 2 month of reagent.