*Oxygen*

[Woodstock]

Ohhhh Boomer....

I am at work and can not find the links to "the need to breath" articles from Advanced Aquarist that may answer this question for me; but whilst my brain is wondering about it, I want to ask the question...

My 90 gal reef is heavily stocked with livestock and the water parameters are excellent! Everything is thriving but I was concerned about the night time hours when the oxygen would be at its lowest... How do we know when our stocking levels of corals/fish/anemone/etc.,etc. are too heavy? Specifically, oxygen levels.

Should I be testing oxygen levels?

[Gibeon]

Woodstock. I looked but couldn't find anything that matched "need to breathe." There was an article on maintaining good flow for corals that is from June this year. Here's the link: Part 1 and Part 2

As for testing. I test my O2 every couple of weeks. It averages about 8mg/L, which is pretty much saturation level for my salinity and temp. All my aeration comes from surface agitation from my canister filter return and a powerhead. I do have a glass top, but the back 2-3" is open. I still need to do a late night test, say 4 in the morning - which I'll have a chance to do on Tuesday when I fly out to North Carolina at 6:00am...

[Boomer]

The Need to Breathe, Part 3: Real Tanks and Real Importance
http://reefkeeping.com/issues/2005-08/eb/index.php

You'll find 1 & 2 at the bottom

A well run reef tank always has good O2, especially with a good skimmer. About 1 % of the people in this hobby test for O2. Even Randy does not test for it. It is nice to know if you want to. The best kit fro price with good accurate readings is th LaMotte. If you want to go nuts then the HACH @ $200.00 and tests O2 to .0.02 mg / l . The LaMotte is .1 mg/ l (good enough) @ $45.00

Gibeon

It averages about 8mg/L,

No way, either you are doing something wrong or the test kit is in error. a @ SSTP it is 6.5 mg / l @100 % saturation. 8 mg / l is 123% at sea level. Your tank would look like a fog bank with bubbles. Your tank "may" peak to that at the highest level during the day for brief period, if you ae lucky.

[Woodstock]

Great info! Thanks! I'll pick up a LaMotte kit asap.

Could you give me an acceptable low end range? I plan on testing first thing in the morning when the levels will be their lowest...

[Gibeon]

Originally Posted by Boomer

Gibeon

It averages about 8mg/L,

No way, either you are doing something wrong or the test kit is in error. a @ SSTP it is 6.5 mg / l @100 % saturation. 8 mg / l is 123% at sea level. Your tank would look like a fog bank with bubbles

123% it is!

Hmmm... well, I'm not at or below sea level. I'll admit that it's a cheap test kit. It definitely showed darker than 5 and looked very near 8 last time I checked. However, it did once show 11 so I will probably toss the kit when I get home. Thanks for the info! BTW, who makes the best (or reasonably good) test kit for O2? Salifert?

[Boomer]

LaMotte http://www.lamotte.com/pages/aqua/testkits.html

I'm not at or below sea level

If you are above level that 123% will be even more, depending on elevation.

123% it is!

Yes, if 6.5 is 100 %, then 8 is 123 % . 8 / 6.5 = 123 %

[Boomer]

Woody

When you buy one try to get it from, them and then get the book;

Labratory Manual for Marine Sceince Studies

[boozeman]

havn't read the articles yet...but was wondering, would a redox probe/reading give you an indirect idea of your o2 saturation level?

[Woodstock]

Ordered both! Thanks Boomer

I also found this information LaMotte - Tips for Testing Dissolved Oxygen

Tips for the testing of Dissolved Oxygen:

Dissolved Oxygen

Oxygen is critical to the survival of aquatic plants and animals, and a shortage of dissolved oxygen is not only a sign of pollution, it is harmful to the fish. Some aquatic species are more sensitive to oxygen depletion than others, but some general guidelines to consider when analyzing test results are:

5-6 ppm Sufficient for most species
<3 ppm Stressful to most aquatic species
<2 ppm Fatal to most species

Because of its importance to the fish’s survival, aquaculturists, or “fish farmers,” and aquarists use the dissolved oxygen test as a primary indicator of their system’s ability to support healthy fish.
Where Does The Oxygen Come From?

The oxygen found in water comes from many sources, but the largest source is oxygen absorbed from the atmosphere. Wave action and splashing allows more oxygen to be absorbed into the water. A second major source of oxygen is aquatic plants, including algae; during photosynthesis plants remove carbon dioxide from the water and replace it with oxygen.
Absorption:

Oxygen is continuously moving between the water and surrounding air. The direction and speed of this movement is dependent upon the amount of contact between the air and water. A tumbling mountain stream or windswept, wave covered lake, where more of the water’s surface is exposed to the air, will absorb more oxygen from the atmosphere than a calm, smooth body of water. This is the idea behind aerators; by creating bubbles and waves the surface area is increased and more oxygen can enter the water.
Photosynthesis:

In the leaves of plants one of the most important chemical processes on Earth is constantly occurring- photosynthesis. During daylight, plants constantly take carbon dioxide from the air, and, in the presence of water, convert it to oxygen and carbohydrates, which are used to produce additional plant material. Since photosynthesis requires light, plants do not photosynthesize at night, so no oxygen is produced. Chemically, the photosynthesis reaction can be written as:

Light + nCO2 + nH2O (CH2O)n + nO2
Light + Carbon Dioxide + Water Carbohydrate + Oxygen



Where Does The Oxygen Go?

Once in the water, oxygen is used by the aquatic life. Fish and other aquatic animals need oxygen to breathe or respire. Oxygen is also consumed by bacteria to decay, or decompose, dead plants and animals.
Respiration:

All animals, whether on land or underwater, need oxygen to respire, and grow and survive. Plants and animals respire throughout the night and day, consuming oxygen and producing carbon dioxide, which is then used by plants during photosynthesis.
Decomposition:

All plant and animal waste eventually decomposes, whether it is from living animals or dead plants and animals. In the decomposition process, bacteria use oxygen to oxidize, or chemically alter, the material to break it down to its component parts. Some aquatic systems may undergo extreme amounts of oxidation, leaving no oxygen for the living organisms, which eventually leave or suffocate.
Other Factors:

The oxygen level of a water system is not only dependent on production and consumption. Many other factors work together to determine the potential oxygen level, including:

• Salty vs. fresh water: Fresh water can hold more oxygen than salt water.
• Temperature: Cold water can hold more oxygen than warm water.
• Atmospheric pressure (Altitude): The greater the atmospheric pressure the more oxygen the water will hold.

[Witfull]

never tested,,prolly never will~

[Woodstock]

I've never ordered hazardous material before... Guess I should order a pair of gloves and goggles too? LOL~

I see the refills can be ordered seperately when needed for only $22 (plus shipping).

[Boomer]

booze

No it will not. pH changes will cause the most variation, if you are not doing anything to the tank, like adding stuff. Then it will really change for awhile. Higher pH will always have a lower ORP and lower pH will always have a higher ORP.

Woody

Allot of those test kits already have allot of so called hazardous materials. LaMotte and HACH are big at telling you what. Kalk is a hazardous material, do to its high pH.

[Woodstock]

Very True!

Is it true that one can't buy pickling lime in Canada??

[billyr98]

interesting topic Woody!

Never tested it.. Why don't you stop over and test mine, when it comes in!

[Woodstock]

LOL! Fly me and I will...