It's been a pain in the butt because the tank's nutrients were already low.
First of all, since the first of January it has been a fishless tank. So I put in a tiny bit of food now and then to feed the CUC. Tests were always 0 for everything until I put the rock in. Then I started getting phosphates. I thought I was just overfeeding the CUC, so I cut back. I added more algae to my HOB refugium, some weeks I'd get 0 and some I'd get a slight hint of phosphate.
Then I added a scooter blenny, which only eats pods. So it doesn't add much to the nutrient level. I started training it, so adding a little frozen food, without rinsing it. Started rinsing it. Added more algae to the refugium. Added more CUC. Tried phosguard. Added some corals that I feed once a week with frozen mysis directly to the heads. So added a little more nutrients.
Still this whole time my phosphates flicker between nothing and something and since I only had the API test, I didn't know how high that something really was. Never was the color of the .25, but was sometimes not the color of the 0.
Finally ordered a Hanna checker and currently I get 0. I get 0 for nitrates, sometimes I get up to 5 for nitrates.
So I really don't think it is the inhabitants or the food I feed. I think it really is the rock. So I've decided to stop chasing it and just let it be. It'll run its coarse and until it does I'll keep any additional frags I put in the tank away from those 2 rocks.