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Re: low ORP in new tank

> Date: Wed, 16 Aug 2000 10:24:02 -0700
> From: Mark Gilmore <gilmore at physics_ucla.edu>
> Last weekend, I set up a new 75 gal tank (no plants or fish yet).  The 
> setup is virtually identical to the 60 gal (CO2, pH control).  I moved the 
> ORP probe from the 60 gal to the 75, and it is measuring approx 220 
> mV.  
> My question is: does anyone know why the ORP is so low compared w/ the 
> established 60 gal tank? Is this usual for a new tank? 

Based on my hazy understanding of ORP...

ORP is measuring the oxidation/reduction potential of the water; it ability to 
alter the chemical state of things. Add a strong oxidizer like hydrogen peroxide 
or ozone, the ORP goes up and nasty things disappear. Reef people who like 
hi-tech use ozonizers and ORP controllers to keep ORP high. 

Plain old tap water has an ORP of around 275 mv (at least ours does). In a new 
aquarium, there are plenty of things to oxidize and reduce - weird bacteria, 
strange stuff on the gravel, etc. It seems reasonable that a newly set up tank 
would have lower ORP since the "potential" is being used up to take care of this 

> Is this telling me anything important?

"Your ORP meter is doing reasonable things". <g>

George Booth in Ft. Collins, Colorado (booth at frii_com)