Hi Chris
Sand substrate (plain old Monterey Bay Aquarium sand). I primarily stopped 3x a week FE dosing because I wasn't totally sure that it was necessary since there is some FE in Flourish Comprehensive and I wasn't seeing any obvious deficiencies in my plants. I had initial target ranges for EI dosing to follow and tweak but no real guidelines for FE dosing. I still add 5 ml about every week or so but am not certain it is needed.