Here's were I got my Iron and Calcium test kits. I plan on getting nitrate and phosphate later this month if I really want. I'm testing less, but the dang Seachem nitrate test is so hard to compare, I want a more reliable test result to taillor my fert regimen.

http://www.aquaticeco.com/index.cfm/...gories/ssid/13

I'm going to get the one that goes up to 10 mg/L. I just have to dilute 1:1 with distilled water and double the results you get. If you need, you could also do a 1:2 dilution or greater and use the appropriate multiplication factor to get your results.