Ozone Usage/Amounts...Iodine Supplementation - 08/30/06 Dear Bob, <<EricR here>> I have a 180g FOWLR.  1 large Emp angel, 1 large majestic, 1 Foxface, 1 Heniochus butterfly, 4 skunk cleaner shrimp. 2 perculas, 1 macaroon, 1 blue damsel, 1 goby, hermits and snails.  The system has been up for 1 year and doing fabulous.  I have 2 wet-dries and use bioballs for media.  2 sump located skimmers AquaC EV-180 and Euroreef RS 130, <<Good skimmers...some authors recommend using multiple skimmers of differing design to optimize the efficiencies re>> One UV 55-watt Aqua UV.  10% water change weekly.  I have started using ozone injected thru the JG fitting of the AquaC and the results are visible: crystal clear water. <<Indeed!  I find ozone to be more efficient than carbon is this respect>> I note that AquaC recommends 50-100 mg/hr of ozone but not more since skimmate production deceases with higher amounts. <<Mmm, yes...and I have read some debate on whether this is desirable or not.  Some speculate breaking down the organic molecules with ozone makes the skimmer less efficient...some speculate breaking down the molecules make the organics more readily available to assimilation by the corals...some say "what the heck", the skimmer is still as "efficient" as it ever was (just has less to skim), the corals "may" be finding more food (just be aware nuisance alga too will have more fuel), so if nothing is being malaffected what is the concern?  I tend to fall in to the latter category I have a Red Sea 200mg/hr ozonizer with integrated controller.  Tank ORP is 315-320mV during the day and rises to 340mV just before the lights go on in the AM. <<Sounds about "ideal" to me>> I have been using 175 mg/hr of ozone in this tank.  At this level the amount of skimmate has gone down from both skimmers. <<I have experienced this phenomenon as well>> The ECV-180 has 275 gal/hr flow rate and the Euroreef system has 180 gal/hr rate. Would you recommend that I go to AquaC's recommended 50 mg/hr? <<Based on your ORP readings and the fact you don't mention any deleterious happenings re, no, I would not drop the production rate that low>> Is it absolutely necessary that the skimmer effluent be carbon filtered? <<No...the amount/concentration of ozone produced by these hobbyists units is easily burned-up in/blown-off by the skimmer>> Would using higher doses of ozone oxidize Iodine or other elements to the point of detriment where HLLE may be a concern? <<Addition of Iodine with water changes is recommended...else test/dose as needed>> Thanks, Have a nice day. <<Same to you my friend>> <<Regards, EricR>>