O2 Question

[oldschool52]

HI guys, my question is a little out of the norm, as usual.
Those who know me know I test with a multiple of Mfgs test kits for just about everything but have never seen much posted on oxygen saturation.

Background:
One of our tanks is a 5 gallon nano set up for Dwarf-Seahorses. We have had 3 spawnings with a 98%-99% successful mortality rate. The tank looks similar to a refugium with all the macro-algaes and gets a 20% water change twice a week. (numbers are good)

Question:
Noticed more of the ponies visible thann usual, babies 1 week, 4 weeks, 8 weeks and adults (didn't have to play "Where's Waldo" with magnafying glass to find them) this morning. Ran a complete bank of tests. All numbers good and did do a 20% water change last night. Checked Dissolved Oxygen last. Normal or good O2 level for salt water with a SG of 1.022 to 1.025 and a temp of 71 to 75 F should be between 7.1 and 7.5. This tank showed an O2 level of about 10.5 ppm. My actual question is.... What would be considered too high a suturation level of dissolved oxygen and why? I'm hoping one of you guys, who have a chemistry and/or especially a better knowledge of water chemistry than I do can answer this. (I'm an Electrical Engineer chemistry never a strong point). If known are there any ill effects on salt water critters in my case specifically seahorses, with elevated O2 levels.

Like always, thanks guys ahead of time.

 

[ichthyoid]

Based on the assumption that your temperature is 25 deg C and at sealevel it would be 8.2 mg/liter, which is the same as ppm. Being in Atlanta we are at about 1000-1100 feet above sealevel, which would result in the saturation being lower, about 8.0. Below is a good reference for this for your entertainment.

http://water.usgs.gov/owq/FieldManual/Chapter6/6.2.4.pdf">http://water.usgs.gov/owq/FieldManual/Chapter6/6.2.4.pdf</a>

I doubt any of us ever get to the saturation point due to limited surface to volume ratio's of the water to air, and limited exchange that results. I would recheck your numbers/test.

 

[jennm]

FWIW...

71F = 21.66

75F = 23.88 C

That may affect Icthyoid's calculations.

I'm tagging along on this one because it piques my interest - but I have no wisdom to impart

Jenn

 

[oldschool52]

As normal, I don't post normal questions just the kinda not so obvious. That's because I want to learn. And as of now the ponies have all resorted to their normal game of "Where's Waldo". They ate and it's "we don't need you anymore till we're hungry again". LOL

 

[oldschool52]

Oh yeh, The info I post in the original post was from the data sheet and instructions that came with a Red Sea Oxygen test kit. I really didn't make up the number of O2 saturation, honest. I'm going to test again, may have introduce O2 by shaking test too much.

 

[ichthyoid]

FWIW-I did not factor in for your salinity (the x-factor/calibration) either.

 

[oldschool52]

After reading "icthyoid's" reply and link it got me thinking. Maybe I shook up the sample with solutions too much. There are actually 4 different chemicals that are used in this test and I shook each a little vigorously. I ran the test again, (the kit is less than a month old), this time I just delicately inverted the sample with each of the chemicals 2 times each, to mix. My end result was much different (performed test twice for verification and repeatability) this time or should I say both times my O2 levels were 6.0 ppm or mq/L. Both readings were taken from different spots in the tank even tough in a 5 gallon cube it's not much different,. This is more of what I expected so a large part of my first test was caused by my testing technique or the lack of one.LOL By shaking the sample, my assumption is, I introduced excess O2 in the water not the true reading since it should not be able to get that high. I would still like anymore info anyone has it on this subject manner. Thanks again guys.

 

[jennm]

Dave, does that mean that your O2 level is on the low side? Or given all the variables, is that what you expected? Earlier you mentioned an expected result of 7.1-7.5 - is that based on the test kit info?

Have you run the test on any of your other tanks to compare levels in your other setups?

This is a good learning thread

Jenn

 

[ichthyoid]

Another link with a more graphic representation of DO and seawater.

http://www.engineeringtoolbox.com/oxygen-solubility-water-d_841.html">http://www.engineeringtoolbox.com/oxygen-solubility-water-d_841.html</a>#

What you measured seems to be about right after factoring in salinity.

 

[oldschool52]

I'm going to read other link and test other tanks as soon as I get some running done. I found out that technique is VERY important using this test kit. I agree that the lack of O2 can constitute a problem, most of my previous O2 issues occurred with a koi pond (1500 gallons), years ago, when I had ponds. Corrected that problem with an 8 foot water fall that was 2 feet across pumping 3500 gallons of water breaking the surface. No more O2 problems there.

 

[ichthyoid]

Amberjack;405620 wrote: Okay, I'm following this one also.

As an R.T., I work with O2 measurments in <u>blood</u> extensively. In blood, O2 is measured two ways, bound to hemeglobin (PO2) or dissolved in plasma (O2 content). PO2 measurements require specialized electrodes or probes and the O2 content is calculated, although it can also be directly measured. O2 content in water can be <u>chemically</u> measured using the "Winkler" method which is very tedious and its accuracy dependent on technique. It measures the precipitate of maganese, iodide and a few other elements to turn the sample brown. This method is not very accurate. Unless there is an artificial source of additional O2, the partial pressure of O2 and O2 content can't exceed 21% and 23 meq/l, respectfully as this is what is available in room air.

Since O2 dissolved in water is dependent on exposed surface area and water movement, I would be comfortable in saying that in no way can you have "too much" O2 in your system. You can have "too little" O2 and that would definitely affect your livestock.

Agreed. 'Azide-Winkler titrations' can be tricky and, like any titration, are prone to technique related variance. I think that is what he discovered. His O2 dropped significantly when he did not shake the vial.

 

[cwalt]

TemperatureFresh Water mg/lSaltwater mg/l°F°CSea Level2,000ft.Salinity @
35ppt sea water501011.310.59.0591510.19.48.168209.18.47.472228.78.17.175248.47.86.979268.17.56.683287.87.36.486307.57.06.2(mg/l = Milligrams per liter) (ppm=Parts per million)
(ppt=Parts per thousand salinity)


And here is a link for a sensor for about 200.00

 

[cwalt]

http://www.vernier.com/probes/do-bta.html">http://www.vernier.com/probes/do-bta.html</a> for the sensor

and the chart did not format right eother , here is the link

[IMG]http://www.hakkoairpumps.com/subcat15.html">http://www.hakkoairpumps.com/subcat15.html</a>

The chart shows absolute saturation points

 

[ichthyoid]

oldschool52;405593 wrote: After reading "icthyoid's" reply and link it got me thinking. Maybe I shook up the sample with solutions too much. There are actually 4 different chemicals that are used in this test and I shook each a little vigorously. I ran the test again, (the kit is less than a month old), this time I just delicately inverted the sample with each of the chemicals 2 times each, to mix. My end result was much different (performed test twice for verification and repeatability) this time or should I say both times my O2 levels were 6.0 ppm or mq/L. Both readings were taken from different spots in the tank even tough in a 5 gallon cube it's not much different,. This is more of what I expected so a large part of my first test was caused by my testing technique or the lack of one.LOL By shaking the sample, my assumption is, I introduced excess O2 in the water not the true reading since it should not be able to get that high. I would still like anymore info anyone has it on this subject manner. Thanks again guys.

Based on your tanks parameters, I would have to say your reading (if accurate) of 6 ppm is very respectable. Considering that the saturation point for these conditions is 6.6 ppm, and that means you are at 91% of saturation.

FWIW- the 'saturation point' is determined by the percentage O2 where the gas diffusing into solution and that diffusing out are in equilibrium (the same). It can't, under these conditions, go any higher as Amberjack alluded to above.

Only 9% to go, what are you waiting for? LOL

 

[oldschool52]

Ok, thanks for the input. Finally got back home and had a seahorse tank emergency. Reason so far unknown but water got a little cloudy and amonia went up to over .5. 2-8week old ponies and 1-1week old pony bit it. Changed 1/2 the water, put in prime, extra carbon and uv. So far some cloudiness gone and ammonia down to &gt;.25 and also put air pump on tank. (I'm going for that extra saturation) LOL Water temp a little high 75F, seahorses (dwarfs) like about lower temps.

When I came home cats had O2 test kit knocked on floor from my desk and all reagent bottles scattered about. Still haven't found test tube but have a bunch of those. Will get some new numbers on other tanks shortly and keep you informed on seahorse fiasco.

 

[oldschool52]

Hey guys seahorse emergency over will post later about outcome and tank testing for O2

 

[oldschool52]

I will post the seahorse panic / emergency in a new thread. All is now well.

O2 Re-test

I tested the seahorse (5 gal), 72 bow (reef w/sump) and 55 gal (FOWLR w/sump) All tanks tested 6 ppm for O2.

Procedures / method used:

Put 10ml of water from tank to be tested in test tube (do not shake up)
Add 5 drops of chemical A (cap tube and invert twice to mix)
Add 5 drops of chemical B (cap tube and invert twice to mix)
Set on table for 2 minutes
Add 5 drops of chemical C (cap tube and invert twice to mix)
Add 1 drop of chemical D (cap tube and invert once to mix)
Color should change to yellow
Continue to add 1 drop at a time capping and inverting once to mix until test sample changes to a translucent blue color - this is the endpoint.
The number of drops of chemical D it takes to turn sample blue is how many ppm of O2 in water.

This is for "Red Sea" O2 test and I am not familiar with other manufacturers on this test. My technique / method seems to work since all of my results agree. I want to thank you guys for your input and will keep researching this subject for my own knowledge. If I find some interesting info I'll post a link.

 

[wizzdumb]

eeny meeny miney moe