Surface agitation amount necessary for gas exchange?

[Subsea]

Because I operated 10KG maraculture growout in a greenhouse, I purchased an oxygen meter to optimize operations. I have several sumpless and skimmer-less tanks that are easy to maintain.

Without an oxygen meter, lower pH swings between lights on/off or increasing pH differential are indications of increasing carbon dioxide ratio to oxygen at night.

NOTE: A healthy IndoPacific reef has a PH fluctuation of 8.2 to 7.90. Low oxygen at night is a serious issue.

I use canister filters as cryptic refugiums. I load them up with reef rubble and never open them up again. In some cases, I use this canister filter to inoculate new systems.

 

[mcarroll]

I've been wondering exactly how much surface agitation is needed

"Some."

Air will saturate the top ~1/8" or so of water, even if it's stagnant.

All we need is water movement to stir that top layer down into the rest of the tank regularly/continuously.

 

[Malcontent]

"Some."

Air will saturate the top ~1/8" or so of water, even if it's stagnant.

All we need is water movement to stir that top layer down into the rest of the tank regularly/continuously.

To test this, I once put a 49 W pump on the bottom of my tank and pointed the output straight up. It was by far the worst performing setup with almost no increase in dissolved oxygen levels. A wavemaker or air stone increased levels by about 2 mg/L for 24 and 3.5 W, respectively.

 

[mcarroll]

To test this, I once put a 49 W pump on the bottom of my tank and pointed the output straight up. It was by far the worst performing setup with almost no increase in dissolved oxygen levels. A wavemaker or air stone increased levels by about 2 mg/L for 24 and 3.5 W, respectively.

... you were testing whether the air saturates the top 1/8 of an inch?

 

[Malcontent]

... you were testing whether the air saturates the top 1/8 of an inch?

Yes

 

[mcarroll]

Yes

I don't know if you have access, but the book "Captive Seawater Fishes.." by Spotte has quite a bit on this.

 

[Malcontent]

I don't know if you have access, but the book "Captive Seawater Fishes.." by Spotte has quite a bit on this.

Are any papers cited or are they just regurgitating hobbyist myths? Sometimes that happens even in professional publications, sadly enough.

 

[mcarroll]

Are any papers cited or are they just regurgitating hobbyist myths? Sometimes that happens even in professional publications, sadly enough.

The internet has a de facto monopoly on regurgitation of hobby myth – even a book about hobby myths wouldn't hold a candle to one day's output on the internet. A book, after all, is limited by its covers where the interenet is unlimited. ;) Which myth are you referring to, BTW?

Some of "Captive Seawater Fishes..." is in Google Books Preview if you prefer to experiment and want to check it out for yourself – there are 20+ subentries for "Aeration" in the index, so some of it will hopefully be in the preview. I'll be interested to hear what you think. I wish they'd do a second edition, but that seems unlikely today.

(For what it's worth, I think every book I have that even bumps into the subject of aquariums goes into the importance of aeration. Just to name two extremes: Gosse handled the subject in his 1853 Marine Aquarium Handbook; a very interesting read to say the least. It's not really my bag, but Chemical Oceanography (Milero) breaks this subject down into eye-watering levels of theory and formulas if you're curious about that.)

From what I can tell, aeration has always been a concern with aquarium keeping. So at least for folks reading books, it's been one of the first issues addressed in most cases. Even Mills' "You & Your Aquarium" gives it a solid treatment (even including specifics for marine).