yes post it. that will be interesting. I knew aluminum reduces quicker than GFO but needs replacing faster. Sounds like there actually may be little difference between iron based and aluminum then?

I use a digital phosphate meter as well and it's currently at undetectable levels (probably due to my iron dosed cheato -just teasing. lol) but I'm not going to replace it until it's up to 0.05ppm. Hopefully it will take at least 5 weeks to get to that point