Large ORP drop

[ThePriceSeliger]

Over the past few days I've experiences a large drop in ORP. It was steady around 410-430 since I set the tank up roughly three months ago. Nothing has died to my knowledge, and the fish seem happy. However, it started to drop when I added my most recent fish(who is healthy), and around the time I started switching salts (from Red Sea to HW-Marine).

I know it's not the actual number, but since it's such a substantial swing that I am relatively concerned.

 

[TJ's Reef]

With it being such a gradual drop I'd suspect just a dirty probe maybe even the new salt forming a precipitate on it.

Cheers, Todd

 

[Randy Holmes-Farley]

The new salt may also be formulated to a lower ORP.

 

[Randy Holmes-Farley]

Other things that might also impact it are a skimmer needing cleaning, more food being provided due to another fish, and accumulation of detritus.