Advanced Supersaturation of Oxygen question.

[aquafarmer]

Supersaturation can be from oxygen and also nitrogen. These articles might help explain it more...

http://www.lumison.co.uk/~dryden/degassing...s_implicati.htm

http://www.in-situ.com/In-Situ/Downloads/p...ssolved_Gas.pdf

 

I'm in aquaculture and gas supersaturation is a big issue, especially with all the pumps and heating of the water. I am primarily culturing seahorses right now and they are especially susceptible to gas bubbles in their tails, skin, and eyes. Degassing units are common on tanks to help break up the water that has been pumped around. The degasser is typically a cylinder with media in it to increase surface area and to help break up the gases.

 

A dissolved oxygen level by itself isn't really going to tell you if your water is supersaturated. You would need several other variables like barometric pressure and temp. in order to calculate the total dissolved gas pressure and from what I've heard it's a scary math equation. There are meters that read total gas pressure (TGP) but they are quite expensive and not really designed with hobbiests in mind. I wouldn't think that the average home aquarium would have to many issues with supersaturation unless you are heating a lot and then have leaky pumps that can allow atmospheric gases into the water that then gets injected into the tank.

 

I hope this was helpful (and made sense) and post if you have any other questions and I can try to answer them.

 

I forgot to address the skimmer issue. I think it would be possible to get supersaturated water with a skimmer if the pump for it was sucking air and then pumping it back into the sump or tank.

 

Christine

[Mr. Fosi]

This is a fun topic and right up the alley of a class I am currently taking.

 

I'm gonna back nautilus on this one (not much of a risky bet, really ), with one caveat: You will likely never run into O2 toxicity problems in a nano. The conditions for O2 toxicity would be difficult to generate & almost impossible to maintain. I commend the LFS guy for thinking of it and taking the time to mention it, but I believe he is overthinking a bit.

 

As nautilus said, O2 supersaturation in the ocean is largely a function of the photosynthesis going on in the upper mixed layer. Wind-driven turbulence & bubble injection also contribute, but they aren't responsible for the bulk.

 

In a nano, it is very likely that O2 will reach supersaturated levels less than an hour after the lights come on. At the same time, CO2 drops through the floor because it is being used in the generation of the O2. I am sure that some of you are thinking, "No duh! That's why my pH is higher when the lights are on! Tell me something I don't know." My point here is this: your tank is not the ocean.

 

There is turbulent mixing going on (read: quick gas transfer in/out of the water) in our tanks, even the ones with minimal circulation. I hypothesize that it would be near impossible to reach a toxic O2 level in a nano because the energy of the system (read: tendancy toward equilibrium) would tend to offgas O2 before concentrations could reach a threshold that could truly be called "toxic".

 

A skimmer (which is a canister of turbulence) would only help this end, IMO.

[Helfrichs Chick]

lol well I cant win! I got a salifert D.O. kit today, it tests at 7, the kit says it should be at least 7. 7?!?!? LMAO, yea like this helps me at all. Ah well I am way to tired to delve into it tonight, but will read some of the info and try to figure out the tests.