low ORP during daytime

[jlinzmaier]

I have a 180 gal reef tank with a 35 gal fuge and 15 gal sump.

I've had trouble keeping my ORP reading up during the day.

About one hour after the lights go out for the day the ORP reading goes up to around 380 which is where I'd like to keep it. When the lights come on in the morning the ORP begins to drop drastically until it gets to about 250-260.

I had a 100 mg ozozizer and I thought an upgrade to a 200mg would solve the problem, no such luck. I'm currently running 220mg ozone (red sea 200mg ozonizer maxed out) and I cannot keep the ORP from dropping during the day.

I do routine water changes.

The ORP drop doesn't seem to be in correlation to any feedings. The only correlation I can find is in regards to the light cycle.

I understand ORP is a highly advanced and technical subject with many factors to take into account. Just wondering if anyone has any idea why I have such a dramatic drop with the lights turning on and how I can correct it.

 

[bertoni]

Hmm, normally, ORP would rise during the day. Have you tried moving the probe, or checking some water away from the tank? I'm not sure how prone ORP meters are to electrical interference.

 

[Fishie Nut]

When you add fresh salt water to the tank the ORP will naturally drop because that is water that is not oxidized by the 03 and has a lower ORP reading than water that has been subjected to 03. Does the drop have anything to do with a water change?

 

[jlinzmaier]

Hmm... This is interesting!!

Bertoni, I took your advice and tried testing the ORP in different spots in the aquarium and seemed to have roughly the same reading. I even hooked up a new ground probe to eliminate any possibility of stray voltage interfering (something I've been meaning to do anyway just haven't taken the time). I kept the probe away from all electrical cords and made sure it wasn't too close to any electical devices that might interfere.

After getting the same reading (approx 270) throughout the main tank, I put the probe in the sump. The reading immediately began climbing and after 15 min it was at 360. I turned down the o3 from 220mg to 150mg fearing that the inaccurate ORP reading could mean that the ORP has been dangerously high since I had been running the o3 at 220mg. After another 15 min of running at 150mg the ORP stabilized at 380mg and the o3 production has been going on and off since that is where I have the set point.

As I did research about ozonizers, I read that the ORP reading can be different in various areas of the tank and sump, but this seems to me to be an innaccurate reading instead of a variation due to location.

What could be interfering??

I do have my ozone reactor in the first part of my sump and I'm testing the water immediately before it returns to the tank. I'd expect the ORP to be a bit higher in this area than the main tank but not a difference of 100!!

I do notice a decrease of about 20 in the ORP when I do water changes but it climbs back to where it was after about an hour. I don't think the water changes are the interfering aspect. It's a direct correlation with the timing of the lights turning on. Once the lights turn on the ORP dips and when they go off it comes back up again.

Any other ideas?? Any thoughts as to why I'd have such a drastic difference in the main tank and sump readings - which one is accurate??

 

[sditch]

Your Tank reading is what really counts. Taking readings from your sump could be misleading as treated water is at higher concentractions in your sump.

I would love to put my pH and ORP probe but my it would not work out for me.

I use Ozone with my ES100 venturi skimmer and noticed the ORP will drop as the pH raises. Also topoff water with limewater reduces my just alittle ORP (durning the day for topoff water).

I see about 30mv diffrent between night and day.

I seems when my PH was in the low range(7.7 - 8.0) is was easier to keep a orp between 350-375. Now that my pH is in the higher range (8.0 - 8.3) with limewater my ORP is maintained around 290 - 320 with the same equipment.

This may also be due to my Ozine unit not using dryer beads, or maybe not.....JMO

 

[Billybeau1]

jl, I would always measure ORP on the main tank.

The reason your ORP starts to drop when the lights go on is simple.

When your light go on, you start photosynthesis, which raises pH.

When pH rises, ORP lowers. It's that simple.

I would not sweat the change. It's quite natural.

I would not get caught up in the number so much as long as it comes back to where you like it at night.

Keeping the number consistent is not as important as seeing the high point once a night.

ORP is very complicated and there are many reasons for it to fluctuate.

 

[JetCat USA]

<a href=showthread.php?s=&postid=10969501#post10969501 target=_blank>Originally posted</a> by bertoni
Hmm, normally, ORP would rise during the day.

normaly it'll drop during the day.

 

[Billybeau1]

<a href=showthread.php?s=&postid=10973022#post10973022 target=_blank>Originally posted</a> by JetCat USA
normaly it'll drop during the day.

Agree

 

[JetCat USA]

glad we can agree on something tonight

just to elaborate, at night the pH is lower, more acidic and has a higher oxidation potential although it shouldn't be 100mv difference

 

[Billybeau1]

Yes, 100 mv is a bit of a stretch

 

[bertoni]

I agree that a pH drop will correspond with a rise in ORP, and vice versa, but 100 mv is a lot. What is the pH change?

 

[jlinzmaier]

Over the next 4 days I'll keep track of the pH and ORP throughout the day and a few times at night to give you an idea of the fluctuations. I'll post after I tally all the info.

Thanks everyone for all your input thus far.

Jeremy

 

[jlinzmaier]

On another note, while I'm waiting to collect some numbers, how does ozone affect alkalinity or alkalinity test kits??

I hooked up my ozonizer around the beginning of September. About a day or so after I got it running I noticed an extreme spike in the alkalinity. The alk in my tank typically ran 3.5-4.5 meq. After I hooked up the ozonizer it spiked to 8.8 meq!!!!!!

After the initial panic, I decided to do some water changes to decrease it and I've been doing 30-35 gal water changes every week. Since then, the lowest I've been able to get the alk is 6.6. Calcium levels have remained constant at 390-420. After not adding anything for over 3 wks, I added some kalk to raise the Ca a bit (it was at 390 and I like to keep it 400-420) and the alk spiked back up to nearly 8.

The corals and fish seem to have no ill effect so I'm assuming the ozone is interfering with the test kit. I use a salifert test kit, is there any chance the alk truly could have jumped up that high within a day or am I getting interference?? Could the breakdown of organics have impacted the tank in such a way that there truly was a major spike in alk?? What should I do now??

 

[JetCat USA]

sounds like you got a bad test kit there.

 

[jlinzmaier]

Same kit was testing fine prior to initiation of ozone.

 

[Billybeau1]

I havent seen any correlation in my tank with alkalinity and injecting ozone.

Must be something else.

 

[jlinzmaier]

Hmm... Maybe it is the kit. It just seems odd how I had such an abnormal reading right after I started using the ozonizer.

Wouldn't you know, I don't happen to have another kit either.

Does Salifert use the same titrant for the alkalinity test in any other kits?

 

[Billybeau1]

Not that I'm aware of.

Most local fish supply stores sell a kit called API (Aquarium Pharmaceuticals Inc.

They are cheap and surprisingly accurate. They will get you to within 1 dkh either way.

 

[JetCat USA]

you can always mix up a gallon of salt water right quick and test it for a comparison.

 

[jlinzmaier]

Great idea Jet cat!!

Mixing right now.

I did find an old IO alk kit in my cabinet. It read the alk to be 3.25meq!!!!! I have no faith in alk test kits. I was having trouble about 1yr ago getting an accurate alk reading. I bought every alk kit I could get my hands on from API to IO to seachem etc... I got readings from 1.0 meq to 6 meq. After I contacted fosters and smith managers to explain the discrepencies all I got for an answer was an offer to return the items - no explanation why there would be such a difference among brands. I found a salifert kit after that and read good things about salifert so I stuck with them. This obviously proves that there kits can have discrepencies too.

I use Reef crystals and I beleive that the last info I read is that freshly mixed water mixed with Reef Crystals at a sg of 1.025 should roughly have an alk of 4.0meq. Anybody else have any info to show any different? I'll mix it and let it sit for 1 hr and see what I get with both the salifert and IO kits.