problem with ORP

[ddboy]

I just made a larger than usual water change. it is 35g in a 150g setup. My ORP was at around 300+, and after the water change, it has dropped to the 170-180 range, and it doesn't seems to go up after a day of ozone. I checked my probe, and it is good, I was wondering what causes this drop and should I be worried. everything looks fine in the tank.
Or may be the ozone unit is bad? it is a red sea deluxe. 100mg. I know my probe is good, cause I ran it in the test solution. Could it be the unit not producing any ozone? but still, shouldn't my ORP still go up in a while after I changed the water

[jtemple42000]

I would think that it would go back up. You did make a big change. The new water could be part of it. I have noticed with mine that if I siphon off the bottom of the tank and stir some stuff up into the water, the the orp goes down for a while.

If you are producing ozone you would smell it.
Are you injecting into a skimmer? Maybe the venturi line is blocked by salt? Dyer needs to be recharged (if you use one?)

I slacked off on my last couple water changes and my redox fell to 260's. I have done 3, 5 gallon water changes (75gallon tank) over the course of the last three days and it is just now getting back up into the upper 280's

I would just keep a eye on it and see what happens.