Agree with Esshup; probably unnecessary for treating phytoplankton and many cyanobacteria species, which are fairly sensitive.
BTW: CUTRINE ULTRA differs from CUTRINE PLUS, with the former already containing d'limonene to assist cell-wall penetration. D'limonene is a by-product of the citrus(peels) and pine industries, and a component within CIDE KICK, KAMMO PLUS and several other adjuvants - in varying concentrations. I don't consider d'limonene as much a surfactant as I do a penetration-aid. It is an excellent grease & wax "cutter" that is sometimes added to dish-washing detergents (it's the lemon-smell in Lemon Joy).

Kelly Duffie
Cypress, TX