so now I'm wondering if something is wrong with the unit. said:
Yeah, I did a double check on my checker too. I just couldn't believe it, but another test kit confirmed.
I was tempted by the lanthanum solutions, but after talking with a chemist that specializes in marine chemistry, I decided against it. His comment was that he knew it is widely used in fish & mammal exhibits, but it's effect on invertebrates is unknown (scientifically) and that unbound lanthanum is quite toxic in general. He said he could think of a number of potential problems that it could cause with calcification--much the same way that PO4 interferes with calcification. That said, I get the feeling he thinks a lot of what I do with my tank chemically is reckless (and I can't really argue that, lol).
The main problem I had with reducing PO4 was that the tank seemed to hit a wall and just couldn't drop PO4 below about 0.18ppm no matter how much GFO/vodka/etc. NO3 has always been unmeasurable. That went on for months. I then started adding potassium nitrate, iron, manganese, and zinc per some recent discussion on RC and information I learned from working with ENC. Over the course of a couple weeks P was down to single digits. Chaeto started growing like gangbusters (over a pound per week). So a lot of things happened at once, and I'm not sure which things are significant. I've stopped KNO3 additions and I'll see if that has some effect.
Worthy of mention is the fact that I don't run a skimmer, use GFO, or dose any kind of carbon (other than food). My solid export is chaeto only.
