@rvitko I am running a Poseidon 220 ozone generator on my 150 gallon reef. I have a Whisper 40 air pump to supply air to the ozone generator. This pump is rated at 1.3 L/min. A little less than what Tunze recommends. I piped it to the ozone port on my 9410DC. I set the dial to #3 which is where I determined it should be set. I put a carbon sponge on top of the skimmer collection cup. Right away I could smell ozone in the room. I lowered the set point to #2 and it seemed like less of an ozone odor. I set it to #1, which is practically off and while it was better, I could still smell ozone. I then took the outlet tubing and ran it outside. The smell went away completely. I hooked it back up to the skimmer and it was back. So I know the smell is coming from the skimmer. Next I installed a "T" fitting on the air line to the skimmer pump and hooked up the ozone to that so that I am now bypassing the anti-over-foaming chamber. I confirmed that the air line tubing was still sucking with the ozone generator air pump on. Now with it set to #1 I don't smell anything unless I put my head right above the skimmer. At #2 I can smell it more but only with my head in the sump area. At #3, I can smell it in the adjacent room. Everything seems to be hooked up properly. I've discussed this with other people with different skimmers and they do not have this issue unless its turned way up. Since Tunze skimmers appeared to be designed for use with ozone, i would think I would not be having this ozone escaping the skimmer issue. Am I missing something? Any ideas on whats going on?