if you have the probe in any section of the tank where there is significant aeration you may get elevated readings from the oxygen in the bubbles or if bubbles are actually sticking to the sensor tip you can get readings like that...otherwise, in an normal aquarium without any oxidant added (ozone or chlorine etc.), usual levels are anywhere from 150-300 mV; any reading below 0 mV is anoxic...you'd know this without the ORP probe yes, it could be that your probe is reading high...not likely that the analyzer is bad; it's almost always the probe...they go bad in 12-18 months generally, depends on make/model/manufacturer; if you bought something that was sitting on the shelf somewhere for 12 months, it may be worthless...is the probe dated in any way? has the sensor tip ever dried out? they need to stay wet at all times or the reading will be off or the probe may be ruined do you have any calibration solution to work with? could be that the probe is sensing properly but not reading in the proper range; you may need to adjust the analyzer down by X mV to read the proper reading or simply subtract X mV from the reading on the analyzer ORP is simply a moot point on many grounds for monitoring...three of the same brand probes hooked up to one analyzer (one at a time) can and will read three different mV readings...it's just the nature of the beast if you are not using ozone or you are not planning on using ozone or unless you plan on using it for some type of denitrification reactor, I don't think it is important to monitor ORP anyway (anyone have information contrary to this?? there may be some critters that are sensitive to high/low mV levels that I am unaware of) -----Original Message----- From: Shane Clays [mailto:[EMAIL PROTECTED]] Sent: Tuesday, June 26, 2001 12:22 PM To: '[EMAIL PROTECTED]' Subject: RE: ORP Wow. My ORP Probe must be way off, because I don't use any ozone. Is it even possible to reach the levels I am reading without ozone? The probe is ran through my Neptune Aquatroller. Maybe it is way off?? Shane -----Original Message----- From: Moyer, David [SMTP:[EMAIL PROTECTED]] Sent: Tuesday, June 26, 2001 9:21 AM To: '[EMAIL PROTECTED]' Subject: RE: ORP ORP is measured in mV below 450 mV in the system with the animals in theory, ozone leaves a residual at 450 mV...residual ozone would do to your animals what the residual disinfectants from your domestic/tap water would do (reason we dechlorinate) however, this is theoretical; if your critters are alive and well without signs of scratching or respiratory distress, your level of 460 mV is probably not above the theoretical 450 mV basically, if you are constantly feeding ozone into your system and you haven't had problems with animals being affected, you probably won't start having problems...unless you decrease the biomass of your system or feed less food (less organic reduction=higher mV levels all other things being equal) does your ORP analyzer/probe control the ozone feed rate in the tank (is it a feedback loop) or is it just measuring what is going on and you are manually adjusting your ozone generator? Dave -----Original Message----- From: Shane Clays [mailto:[EMAIL PROTECTED]] Sent: Tuesday, June 26, 2001 11:11 AM To: '[EMAIL PROTECTED]' Subject: ORP All, What do those of you who monitor your ORP try to keep it at? Mine is at about 460, and I don't know if that is good, bad or what. I have not found anything in my books to really help me out... TIA, Shane C. ________________________________________ LEAVING THE LIST ================ To stop receiving messages you will need to send a message to [EMAIL PROTECTED] with a command to remove you from the list. The list manager controls who belongs to the list. 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