30 inflowing water 31 is pumped into ozone distribution piping 32 into which is also injected ozone from an ozone generator 33 prior to exposure to ozone the water may be exposed to at least one of ultraviolet radiation and acoustic energy 43 following passage through an ozone injection diffuser 34 the water proceeds via transfer piping 35 into multiple ozone contact chambers 36 three are shown here but this is not intended as a limitation when fully ozonated the water exits via discharge piping 37 in either of the above described embodiments an additional step may be taken of adding a pesticide to the algal colony for controlling insects the pesticide may be selected for example from a group consisting of an insecticide a pyrethroid or a natural pyrethrum although these are not intended as limitations in a particular embodiment the pesticide may comprise bacillus therengensus isralioans bti a further element of either of the systems 10 30 shown in fig1 comprises a bti culturing system 40 wherein bti is substantially continuously cultured or cultured as needed and a continuous drip of bti is provided via line 41 leading to drip hose 42 adjacent the inlet 23 of the periphyton bed 24 as an additional or alternative embodiment further systems and methods are envisioned for detoxifying one or more elements of the system 10.