I'm telling you, mine is screaming now. I dose a ton of AFR, 40 ml a day. That's holding my alk around 9.5 +/-.5. all of that alk means I need nitrates, quite a lot of them. So I was dosing up with kno4 until Randy told me I was gonna bork my tank by raising potassium to high. So I backed off and used ammonia bicarb instead. Nitrates have been hovering right at 10 and holding without added ammonia. Just regular feedings now. I need to do the whole array of tests tonight. Probably phos is creeping up around 1.
On that par meter thing. Keep an eye on ebay and growers forums. Apogee Sq-420's turn up for about half price from time to time. I think they are around 250 new. I have to apply about a 8% correction on par. Because this one is for "flowering plants", it is looking for a slightly different spectrum. But it's been the most invaluable tool I don't lose coral anymore.