I check parameters about once a week. Even though I'm fairly diligent about my tests, I have an AWC system that I swap between the reef and FOWLR tanks every couple of weeks or so. My parameters tend to shift just a little bit as a result, but so far everybody seems okay with it. Someday I'll set up a second dedicated AWC, but I'm okay with doing it like this for now.
As vetteguy said i to let my reef tell me what’s going on. Test maybe once a week just to be on the safe side. I dose AFR daily and for me AFR keeps everything where it should be. Occasionally a small dose of magnesium is needed to boost it up closer to 1400 where my corals seem to like it.
I hardly ever test. If everything's growing and looks healthy and clean, then she's all good
Plus only a nano 25g and my biweekly water changes would be 25% which helps keep everything in check
I have done it both ways since I am in this hobby.
Many years I had no tests and I was just paying attention to the corals if they were happy.
I bought tests less than a year ago and now I check my parameters occasionally.
I had good results with both methods.
My tank's 18 months old, and since day 1, I've performed regular testing to ensure my water follows the recommended reef tank parameters I found here on reef2reef.
I invested in an Apex controller with the Trident, which does four tests daily. I've found owning the Apex system fascinating as it shows me my tank inhabitants' daily demands, making it very easy to add/remove any supplements as required.
I also use Hanna checkers for phosphate and nitrate, which I use weekly.
I've never suffered any algae issues since starting my tank, not even diatoms when the tank was new. When the tank was young, I had to dose phosphate and nitrate into it. Now it's a bit more mature, all I need to add is a small amount of GFO which keeps the phosphate level in the sweet zone.
Testing my tank regularly puts my mind at rest and makes it much easier for me to understand what's going on. I can easily dial in very minor adjustments to tightly balance it.
The one thing I've never understood is "don't go chasing numbers"? I've read hundreds of posts on here, explaining how important it is to keep tank parameters stable. Just about every successful reef keeper doses additives, some use calcium reactors and a whole heap of other things to keep their tank water params stable. Surely that's chasing numbers?
So, I work away for months at a time! The Trident takes care of the three big ones for me when I am away (closely supervised by the missus!). ICP's are going in every three months or so (triton) when I remember.
When I am home, I test manually once a week for alk, cal, mag, no3, po4, pH and salinity. Religiously. Is it sad that I really enjoy that?
When I am away, it is being done somewhat intermittently- she has her own three nano tanks to tend to as well which tends to hold priority over my tank that has got all the automation and stuff on..