Oxygen In A Skimmerless Tank?

[dpearly88]

Is it safe to run a reef tank with out any method of oxygenation (air pump/skimmer)? Or is surface exchange enough to maintain oxygenation?

[Boomer]

I may be enough it depends on how much gas exchange you are getting. Noramlly it will be lower.

[awestruck]

Hi Boomer, I have a question. When gas exchange occurs, does it happen because the water is moving at the surface or just because the surface of the water is meeting with the air? TIA

[Boomer]

Both, it is a very complicated issue. But it is mostly due to water movement. Also allot depends on the CO2 in air gas pressure and the CO2 in water pressure. These are called Partial Pressure of the air and water. The higher the air partial pressure the easier CO2 or O2 inter solution. If the two pressures are equal nothing really takes place.

[awestruck]

Hi Boomer, thanx for your response. :) I use a spray bar for surface agitation and I think it does a good job. I have no idea how to test for oxygen levels though, thus I am just guessing. Additionally, I try to get our windows open whenever it's not too cold outside (I live in Wisconsin and have been known to tell my son to put his coat on because we need fresh air in the house! :) ) Does this sound like I am getting good gas exchange in my tank? TIA

[Boomer]

Spray bars w can work nice. You will know if there is not enough O2 the fish will tell you :lol: Also those hanging box filters that drop water like a water falls work nice. You could get one of those and just do not put anything in it, just use the waterfall effect.

[vessxpress1]

Awestruck: Salifert makes an O2 test that's about the same price as their Ca tests. I decided to get one just out of curiousity.

The test recommends 8 mg/L O2 for freshwater and at least 7 mg/L for saltwater.

I went back to a HOB filter, skimmer, and Phosban reactor running 24/7. I have a lot of surface agitation and pumps on a wavemaker. The highest reading I got with the kit so far was a 12 during the day.

At night, my pumps go off, but the filter and skimmer remain on and it slips down to 8 mg/L. Which is ok but I was kind of surprised. I know there's no more photosynthesis happening in the dark but it would seem like the skimmer would be infusing so much oxygen into the water that it would maintain 12, but it doesn't.

If you have no HOB filter, skimmer, or little or no surface agitation, I would imagine a tank could have serious O2 issues over-night.

[Boomer]

vessx


There is something very wrong with those values it is impossible for a reef tank to get 12 ppm unless you are adding pure O2 from a cylinder. All things in the tank would be cover in bubbles and at 12 some marine life may even be under stress. 12 ppm in saltwater is almost 200 % saturation. Even your 8 ppm is not believable, as that is almost 130 % sat.

NSW at 35 ppt and 82 F is only 6.4 ppm at 100 % sat and most tanks do not have even that. Good reef tanks get to over 6 and in some cases may reach higher than 6 during certain parts of the day. When you, a LFS or bait dealer takes a small bag and fills it with O2 to transport fish and corals it still is not at 200 %.

Here is a table for you and this is at sea level. If you are above sea level it is even lower and if there is a low pressure area, as in a weather front, it is even lower.


http://www.pisces-aqua.co.uk/aquatext/tables/oxygen.htm

Here is a calculator that takes all in account except atmospheric pressure shifts from weather fronts. These values you get in mg /l or ppm is at 100 % sat. At 1000 feet, temp at 28 C (82 F) and a Salinity of 35 ppt = 6.2 ppm 100% sat

http://www.aquanic.org/images/tools/oxygen.htm

Salifert has had lots of problems with that O2 kit. I do not know why and/or you are running the test wrong. For years I ran O2 test with a very expensive kit and O2 meter and never got even close to 12 ppm or even 8 ppm except at peak times of the day I would get 8. And these were all very high tech reef tanks with massive flow rates, excellent water/air gas exchange and big skimmers and the tanks filled with corals and refugiums with marco's.

You are much better off getting a Lamotte O2 kit, which test within .1 ppm O2 and it does not cost an arm & leg :D

Here is an old post of mine were we discuss O2 equations

http://reefcentral.com/forums/showthread.php?s=&threadid=120213&highlight=barometric

[awestruck]

Hey guys---well, my protein skimmer is a HOT because I have no sump thus I am getting surface agitation from 2 sources: the spray bar (as I previously mentioned) and the skimmer which kind of performs the waterfall effect while simultaneously skimming. I have never seen my fish gasping so I assume there is enough oxygen--plus, again as I previously mentioned, I do open the windows several times a week to ensure that fresh air is coming into the house. However, I would like to check the oxygen level simply out of curiosity.

[vessxpress1]

Hey, thanks Boomer. Interesting. Yeah, I compared the colors the best I could and I know it read 8 the last time I did it. I'll have to try it again during the day and see.

It says not to shake the test vial as that could add more O2 to the test and give a false reading. I don't shake it but I wonder if you swirl it too hard if it adds O2 to the sample? That could be a possibility.

There's 3 seperate bottles of drops that you have to swirl in. Knowing this, I'll have to try another one and try to swirl it very softly.

[Boomer]

I have never played with Habib's O2 kit. Swirling yes the same thing but not as bad. Does his test procedures talk or mention "fixing" the sample ? A LaMotte kit and some HACH like the really expensive HACH on I had use titrators, a syringe, just like some Alk kits yes. You count the drops until there is a sudden color change, called "end point" and the number of drops = the ppm O2 by formula or you look at the number on the syringe = ppm by formula.

[vessxpress1]

Just re-ran the test right before lights out and I was extremely careful this time not to swirl the sample too hard.

This time, the color matched up at 6 mg/L. Which before your posts, I would have been worried but sounds like that would be more normal now.

The Salifert kit doesn't use a syringe for any of the chemicals. There's three chemicals and they're all in the small squeeze bottles.

You add 5 ml of water to the test vial.

Add 4 drops O2-1 and swirl 'gently' for 20 seconds.

Add 4 drops of O2-2 and swirl gently for 15 seconds. Allow to stand for 3 minutes.

Add 4 drops of O2-3 and swirl for 5 seconds after each drop. Then allow 1 minute for color development. It goes from clear to a shade of pink. You compare it to the chart.

[Boomer]

Ok that is more like it ;)

Get a LaMotte were you are not comparing against a chart.