Orp

[maxpc99]

I agree.. His ORP probe needs to be calibrated or is defective.

I use ORP but only for trending and alarms via my Apex. I can tell from my ORP if something has gone wrong or died. I don't look at the number as much of an indication unless it changes fast. My number averages 325-350 depending on the time of day.

This!

Last September I bought and installed an orp probe. One week later my tank crashes because I foolishly moved my basement sump cheato light (home depot flex hinge shop light) from its safe perch to an overhead floor joist. Of course it fell into the sump and cracked leeching god knows what into the water. I didn't make the discovery for a solid 12 hours, but if I had an ORP alert set up I would have known immediately and would have been able to minimize the damage. ORP dropped from 425 to 200 almost instantly. Net result I lost 50 + sps colonies and frags.

 

[maxpc99]

....

FWIW, aquaria with refugia often run a lot lower in ORP than similar aquaria without them. But that doesn't mean, IMO, that the refugium is undesirable.

So this is most likely why my ORP has dropped! I was always in the 420 to 390 range and now I'm low 315 to 285. I never let it bother me, but was in the back of my mind that something was up. I added a 40b fuge with DSB and full of macros.

Why would a fuge have that impact?

 

[Mylesweaver]

I don't like refugiums, I've tried them and don't like the results. I grow bacteria. It's much more efficient and does a better job. If my nitrate and phosfate get high more bacteria live so my orp drops, when my tank is clean ( low nitrate and phosfate) less bacteria live my orp goes up. I believe this number deserves it's place in this hobby.

 

[tmz]

I do both: encourage heterotrophic bacteria via organic carbon dosing bacteria and run a variety of refugia.

Why would a fuge have that impact?

More organics from detritus buildups and algal exudates ;possibly excretions from other fauna like sponges, pods, etc. None of which are necessarily bad things on balance. Nitrogen reduction in a fuge could also have an effect.

 

[Randy Holmes-Farley]

I don't like refugiums, I've tried them and don't like the results. I grow bacteria. It's much more efficient and does a better job. If my nitrate and phosfate get high more bacteria live so my orp drops, when my tank is clean ( low nitrate and phosfate) less bacteria live my orp goes up. I believe this number deserves it's place in this hobby.

Better than what? I grow bacteria too, by dosing vinegar. One of the reasons I have the refugia is to provide a lot of rock surface area (both aerobic and hypoxic) where the bacteria can grow.

FWIW, neither nitrate nor phosphate has an direct impact on ORP, so i don't see how you can judge them to be rising by ORP.

 

[Randy Holmes-Farley]

So this is most likely why my ORP has dropped! I was always in the 420 to 390 range and now I'm low 315 to 285. I never let it bother me, but was in the back of my mind that something was up. I added a 40b fuge with DSB and full of macros.

Why would a fuge have that impact?

I'm not sure, but I think Tom's explanation makes sense.

 

[Mylesweaver]

The more bacteria in the system the more oxygen is pulled out of the water so the lower orp less bacteria less oxygen is being used orp goes up. You can kill a tank if you dump a bottle of bacteria in. Your oxygen level will plummet and so does the orp.

 

[wolfblue]

ORP probes only last so long on the shelf or in use. A new probe can be trash out of the box because its already old. The probes I use at work (Signet 3-2757-WTP) have a install by date on them. On RC, here people say they last a year. At work my probes cost around $400 but they last a long time. 18 months is a long time. They calibrate great at 17 months and by 19 months the junction is just gone.

They can also be broken(cracked or leaking) but they still put up a number. A wrong number that still might be believable. And they can stick at one value. All good reasons to calibrate at two points.

At home if your not using ozone the number doesn't matter. You just look for the drastic changes. You clean and calibrate once in a while to make sure the probe reacts to changes. You put it in at 350 and weeks later has drifted to 430. You know it its probably only 350ish still. You realize that a dirty probe reacts slower but it still moves fast enough to know that fish you have not seen must be dead. And still fast enough when(heaven forbid) a hot lamp gets submerged and bursts.

 

[Mr sea water]

You may get 290mv with out ozone , it will go up with Pergen, a large UV bank or the sun. Running in the 400s will take out the bacteria out the system and I have found I have need to change all the water but it is NSW and free so no issue.

 

[wolfblue]

You may get 290mv with out ozone , it will go up with Pergen, a large UV bank or the sun. Running in the 400s will take out the bacteria out the system and I have found I have need to change all the water but it is NSW and free so no issue.

290 is fine. Eyes count just as much and probably more that mV's. I've seen crystal clear water at 230mV. As far as the 400s taking out bacteria and changing all the water. Maybe if you approach those conditions again you could run some plate counts and help track that one down for us.

 

[Mylesweaver]

I change filter sock every day clean my skimmer cup everyday use coral snow 2-3 times a week change carbon once a week dose bacteria once or twice a week change gfo once a month

 

[Mr sea water]

290 is fine. Eyes count just as much and probably more that mV's. I've seen crystal clear water at 230mV. As far as the 400s taking out bacteria and changing all the water. Maybe if you approach those conditions again you could run some plate counts and help track that one down for us.

Sorry some plate counts do not no what you mean?

 

[tmz]

If my nitrate and phosfate get high more bacteria live so my orp drops, when my tank is clean ( low nitrate and phosfate) less bacteria live my orp goes up

Heterotrophic bacteria may wax( increase) if nitrogen (ammonia, nitrite, nitrate are higher) only if organic carbon, soluble reactive phosphate and a some other elements like iron for example aren't deficient and limiting. Why do you think bacteria reduce ORP?

Nitrate,NO3 is oxygen rich ;it's not a reducer;it's an oxidizer. Reading Randy's article which Jonathan cited earlier clears up a lot of misunderstandings about ORP.

Nitrate contributes to higher ORP;it does not lower it .

BTW, the bacteria encouraged by organic carbon dosing take up ammonia preferentially and then nitrate for nitrogen according to the litterature I've read. With heavy feeding , there is likely plenty of decay and ammonia as well as some nitrate to provide the nitrogen they need.

 

[Raul-7]

So this is most likely why my ORP has dropped! I was always in the 420 to 390 range and now I'm low 315 to 285. I never let it bother me, but was in the back of my mind that something was up. I added a 40b fuge with DSB and full of macros.

Why would a fuge have that impact?

Do you use ozone?

 

[MMM33732]

With that non-ozone 400+ range, try soaking the probe in vinegar for a few min. I use ozone, but notice my ORP rises a little each day (even if ozone is off). Once I clean the sensor in vinegar, it drops back down and the cycle starts over again of slowly rising as the sensor gets "dirty". I have to clean mine about every week and even then it still drops about 50-80mV every time I clean it.

 

[tmz]

The more bacteria in the system the more oxygen is pulled out of the water so the lower orp less bacteria less oxygen is being used orp goes up. You can kill a tank if you dump a bottle of bacteria in. Your oxygen level will plummet and so does the orp.

At the extremes a bacterial bloom from excess feeding etc could reduce O2 to perilously low levels with some measurable effect on ORP. There are other factors involved; aeration for example as well as the interactions between oxidizers and reducers in a particular aquarium.. Inferring the O2 concentration from the ORP reading can be misleading. Do you measure O2 levels?

This is from Randy's article on ORP cited earlier:


Why does the ORP not change more when the concentration of oxygen is changed so much? The simple answer is that equilibrium ORP is just not very sensitive to small changes in the concentration of oxygen. After all, ORP only varies over about 1000 mv from the most oxidizing to the most reducing environments found in natural waters. But the oxygen concentration might vary by a factor of 10[SIZE=-1]⁵⁰[/SIZE] or more.
Keep in mind that ORP is logarithmic in the same sense that pH is logarithmic. If you double the [H[SIZE=-1]⁺[/SIZE]], pH only drops by about 0.3 pH units. In the same way, doubling the [O[SIZE=-1]2[/SIZE]] has only a fairly small effect on ORP.

will deplete oxygen, an oxidizer. However, the relationship between oxygen levels an

 

[billsreef]

Sorry some plate counts do not no what you mean?

He's referring to a microbiology lab method for growing bacteria on a "plate", aka petri dish filled with a special media for growing bacteria. It's a way of determining bacteria counts by seeing how many colonies of bacteria grow on the plate.