I used Randy's 2 part (actually 3 part with the Mg you need to add - don't forget that part or you will end up low in Mg) for a couple years. Easy to do, cheap, and worked well with a 2 channel dosing pump. One note is that you need to do water changes and watch the salinity because the 2 part will raise salinity and you aren't adding any of the other elements and trace elements.
I just recently switched to a Ca reactor because I was tired of mixing the 2 part every couple weeks, but the 2 part was working fine.