Dissolved Oxygen Importance

[Tom Richardson]

We use a mag drive 2400gph small pump connected to an oxygen concentrator.  This small system (with our patent valve) will maintain a 50,000 gallon fish tank for $1/hour @10ppm D.O.  It can go as high as 28ppm D.O. for agriculture purposes.

We also offer 400gpm (500,000 gallons/day) oxygenated water pumps for salmon farms.

Plants can utilize up to 22ppm D.O. at the root level.  Low oxygen levels enables the growth of root pathogens in plants, so higher D.O. levels is extremely important. Many people let the plant roots dry out often to get oxygen to the roots.  We find that you cannot overwater plants with high D.O., in fact the plants thrive. Last week we had heavy rain for several days straight, my plants, tomatoes etc were water logged. I knew it would take days of sun to dry out the roots. Instead poured lots of oxygenated water on the plants and they lost their 'droop' within a  few short minutes.

Fish cannot take more than 12ppm D.O.  Any higher and they get an air embolism around their eyes.  However fish need D.O. for digestion, for example we have clients that operate dozens of salmon farms.  When the D.O. goes below 6ppm, the fish stop feeding, resulting in massive loss of growth.

If you grow your plants using a volcanic rock base medium, the medium will actually thin the water as it percolates down.  By the time the 22ppm D.O. water reaches the bottom of the plant, it only has a 9ppm D.O. level.

To conclude, we are testing this for aquaponics, it offers a way to grow plants faster using oxygenated water, and maintain healthy D.O. levels for bio aquatic life.

Our greenhouse customers, aquaculture clients see big gains with oxygenated water.  Aquaponics is a perfect fit.

[TCLynx]

There is a such thing as super saturation which would be bad for fish, however, you can't get super saturation with just water splashing in shallow tanks or a regular atmospheric air pump bubbling through an air stone so no worries there.

Super saturation would be like if a pump under some extra pressure was getting some air bubbles through a seal, it could possibly cause some micro bubbles which could be dangerous.

Otherwise, super saturation is highly unlikely for the average AP system provided you are not using pure oxygen. As soon as you start using pure compressed oxygen, the rules change.

Another thing to keep in mind is that the saturation point for dissolved oxygen in water is highly temperature dependent.

[TCLynx]

Kobus Jooste said:

Let me rephrase, as it seems as if my attempts to be brief always results in my question being used as an opportunity to lecture me.

Kobus, Not lecturing you, getting you to share more so I can learn from you!

In my reading, so far the only examples I've heard of that might super saturate had to do with a pump sucking in some air bubbles and under pressure forcing them to dissolve or introducing air under high pressure circumstances. Like where a damn might release cold bottom water to cascade down into a river causing problems for fish not only with the temperature difference but also with the water plunging under pressure down in such a way that it might cause super saturation. (Sorry I don't really under stand the details of this one so I probably got it a bit wrong.)

My comment was mostly to let people who don't know much about it, know that they should do some additional research before simply pumping oxygen into their fish tanks.

Now I hope you get some answers to your questions there Kobus because you have made me curious. And how is it you are keeping such high dissolved oxygen numbers? Do you have some pictures of your cascades? I don't have any really good way to measure my dissolved oxygen numbers as I hate to pull out the test chemicals too often since they are mostly somewhat dangerous to handle. I did run a test not too long ago after I had the water pump off for a few hours and my levels were still in the "safe" range for my fish and none were at the surface looking for air. I have not run any tests when the situation should give me the "highest" readings but didn't figure I needed to worry about it with only the air stone and the spray bars I didn't think I would be risking making it too high.

[Tom Richardson]

KJ I think you are right on. I use a $1200 D.O. meter which reads up to 100ppm. The water here in Victoria, BC is 8.7ppm., same as your water readings. Here's something interesting; we can saturate oxygen in seawater up to 65ppm, but only 40ppm freshwater, by recirculating for 2 minutes in a 50gal barrel. I believe the oxygen molecule binds slightly to salts. Water only loses 2ppm oxygen per day, even exposed to sun, wind, due to the fact we do not bubble water, nor micro diffuse, we exchange gas (O2) into liquid (water). The reason we use compressed oxygen is we deal with large volumes of water, working in the farmed salmon industry. Our patent is a 10" x 2" pipe (valve) that spins pumped water and injected oxygen, and comes out at 80gpm at 18ppm oxygen. Recirculated in a closed system it will rise to 65ppm quickly and stay at high levels for weeks. We are now making sized down valves that screw onto small mag drive pumps for use in big hatcheries. A 30gpm submersible mag drive pump with our valve attached, hooked up to an oxygen generator, will maintain a 50,000 gallon system, for less than $2/day. Our small system replaces the need to buy larger systems, requiring liquid oxygen, with a cost of tens of thousands. The same pump is installed in large greenhouse operations. A single pump/valve will oxygenate water to high levels accommodating 10 large commercial greenhouses.

For aquaponics, our small pump/valve and oxygen concentrator will lease for $200/month to operators.

Oxygenated water makes an incredible difference in plant growth with more than a 25% increase in plant size and speed to harvest. We are close to companies such as Terrasphere www.Terraspheresystems.com who have patents in vertical farming systems using LED lighting. Their system grows 4,000 plants such as lettuce, sold to markets, in a very small space. I need to figure out how to deliver oxygenated water to aquaponics plants at 22ppm D.O., then thin the water to lose oxygen for supplying into the fish tanks. Volcanic rock medium does this very well as the rock is so porous and has a large surface area.

We would like to help make systems that enable urban farmers the ability to make aquaponics a serious commercial venture for anyone to get into. If you can maintain the proper oxygen, anyone can be successful with aquaponics. I hope we can keep this dialogue going and I would be happy to report more as tests are finished if you are interested.
Cheers, Tom Gaia Water www.GaiaWater.com

[Harold Sukhbir]

Good article on DO.

http://users.vcnet.com/rrenshaw/do.html