been using Seachem pH buffer and works like wonder.
tried the Kent Marine Iodine and works too well for me- algae boom just after few days of usage and bear in mind, i always start off with 25% of what is recommended!!! so switched to Tropic Marine, been a yr liao and working fine!
Kent Turbo Calcium - very effective but that was before i switched to Ca Reactor. but price wise it is on the high side.
Kalkwasser - AquaZ coz back then got discount, bought in bulk, easily last me 1+ yr!
Phytoplankton - switched from DT to Aquatim, no visible changes though .....