ORP Dropping?

[bluespotjawfish]

My tank's ORP is typically over 400.
A few weeks ago I noticed it was in the mid 300s.
This morning it was down around 300.
Today post water change it is about 290.

I need help determining the possible cause.

ORP Probe on Aqua Controller gone bad?
Tank trying to crash?
?????

The 150g tank has been established for just over a year.
Last week I did a 40 gallon water change w/Red Sea salt.
Today I did a 25 gallon water change mix of IO and RC.

Alk 180 ppm
Calc 400 ppm
Mag 1350 ppm
Temp 78
pH 78.5
Nitrates 0
Phosphate 0
Salinity 1.026

Thoughts, suggestions?

 

[DaveK]

Measuring ORP is a funny thing. Many things can throw off the reading. Just putting you hand in the tank can do it.

If the probe meter, and everything else is OK, a fall in ORP generally means the system has more pollution to deal with. This can be in the form of livestock dying or from an increase in livestock.

Water changes will also temporarily lower ORP. So don't panic, and see what it is the same time tomorrow. If it's higher, your ok,

How old is your ORP probe? They should be replaced annually, or sooner if the stop working or give funny results.

As of now, I'd wait ans see. You may not even have a problem. One key indicator is how does the livestock look? If it's doing great, don't do too much to alter ORP. If the livestock "just doesn't seem right", then you want to take some action.

 

[bluespotjawfish]

ORP is 265 this morning.

I have had some losses. I have had a very tough time keeping my alk/calc/mag to the correct levels lately so I had attributed the losses to that.

 

[Boomer]

A drop form 400's to 200's is a good sign of things no going well and some thing is dead, dying or large release of something or something was added to the tank. If you have had some losses that will explain it.