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#1
Enigma

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I did a quick forum search and couldn't really find much on oxygenation, so I don't think this has been beaten to death. If it has, please accept my apologies if I've missed something and am beating a dead horse. :)

I'm running a (very newly setup) 10 gallon system with a glass top. I've got a Fluval C2 filter that moves a lot of water. I feel that the water moving through the filter system should be picking up enough oxygen to keep the tank healthy. Is that the case?

For the sake of adding some interest and movement to the aquarium while it goes through the initial cycle, there is a bubbler in it right now. I don't plan on leaving that in there (it is a bit cheesy), but I'm wondering if a bubble stone of some sort would be a good idea when I pull it out?

Edited by Enigma, 21 March 2012 - 12:39 PM.


#2
seabass

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The ocean's reefs are near oxygen saturation levels. Our tanks, even with a decent skimmer, don't reach these levels. It's not so much that air stones are cheesy, as the popping bubbles will cover your equipment with salt creep. Most people rely on a skimmer for improved oxygen levels.

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#3
Enigma

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The ocean's reefs are near oxygen saturation levels.


Most excellent to know. Thank you!

Our tanks, even with a decent skimmer, don't reach these levels. It's not so much that air stones are cheesy, as the popping bubbles will cover your equipment with salt creep. Most people rely on a skimmer for improved oxygen levels.


Sorry. I meant that the light-up disk bubbler thingy (how's that for a technical term?) that I've got in there right now is cheesy. I'm not going to let that stay. :lol: I find the bubbles stones a lot less offensive.

How do the filter and the skimmer compare for improving oxygen levels? It is a possibility that I'll remove the filter from the tank and go with a skimmer instead (though the filter may just be moved to the sump . . . if I build one).

#4
seabass

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How do the filter and the skimmer compare for improving oxygen levels? It is a possibility that I'll remove the filter from the tank and go with a skimmer instead (though the filter may just be moved to the sump . . . if I build one).

An HOB filter will improve surface area and agitation. This will help gas exchange (and therefore oxygen levels).

A skimmer uses lots of tiny micro-bubbles (normally designed to maximize bubble contact time with the water). This is a superior method of gas exchange, and an often unspoken benefit that skimmers provide (along with pH stability due to the release of CO2).

However, a skimmer is not necessary. Also, a skimmer will normally not oxygenate water to the point of supersaturation as is often found in nature.

It's an interesting topic that is often overlooked. Some people are even experimenting with more controversial methods such as dosing H2O2 or ozone. However, I'd stick to the tried an true (like a skimmer).

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#5
Whys

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Placing algae, such as Chaeto macro-algae, in a separate compartment, such as a refuguim, then setting it's light cycle opposite that of your display tank, will help to maintain higher oxygen levels throughout the system at night.

Edited by Whys, 20 March 2012 - 09:54 AM.

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#6
seabass

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Here's a series of articles on the subject:

The Need to Breathe in Reef Tanks: Is it a Given Right?
The Need to Breathe, Part 2: Experimental Tanks
The Need to Breathe, Part 3: Real Tanks and Real Importance

Chaetomorpha Discussion
Perhaps most interesting were the results of illuminating small tanks containing a handful of macroalgae. In the previous article, the fifteen-gallon tank described above used the same clump of Chaetomorpha that was described in this article. In the fifteen-gallon tank made hypoxic through the use of nitrogen and illuminated by a single 15-watt fluorescent lamp, little oxygen was provided to the tank by the algae. In the ten-gallon tank described in this article, the irradiance was provided by a 65-watt lamp. So long as water flow was provided, the tank increased its oxygen content only minimally, and it is hard to say if the same increase would have occurred without the algae. Once the water flow was turned off, however, oxygen levels rose quickly. I believe this occurred because the water flow caused much of the oxygen produced by the algae to be lost at the air/water interface. With no other organisms present (besides, obviously, any microbes present), oxygen levels remained supersaturated in the tank over many hours; longer, in fact, than I would have expected given gas exchange at the surface. The reduced effect seen previously in the fifteen-gallon tank probably resulted from irradiance levels that were inadequate to maximally stimulate photosynthesis. This experiment shows algae's potential under sufficient irradiance and slow flow, such as the conditions found in refugia, to effectively raise oxygen levels in tank water.


Edited by seabass, 20 March 2012 - 10:32 AM.

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#7
Whys

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Ha! A real argument for a slow-flow fuge, at last! :]

Nicely done there seabass. That is excellent info.

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#8
Reefmaster1996

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Ha! A real argument for a slow-flow fuge, at last! :]

Nicely done there seabass. That is excellent info.

Also important, micro bubbles produced by air pumps irritate fish and corals skin. Stressing them out. How would you like to feel itchy all the time?

#9
PinkDamsel

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It hasn't been mentioned yet but some believe the fact that cooler and lower salinity water holds oxygen better is a reason to keep temp and salinity a bit lower than on a natural reef.

I don't know enough to weigh in either way.

Edited by PinkDamsel, 21 March 2012 - 12:12 PM.

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#10
Enigma

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Lots of great info here, folks! Thanks so much. :) It gives me a lot to mull over.

#11
Whys

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Link

Aquaria can and do become hypoxic at night...

Aquaria can and do become saturated or supersaturated with oxygen during the day, and this is a result of oxygen resulting from irradiance of photosynthetic organisms. In no case was saturation or supersaturation measured without photosynthesis.

Airstones and skimmers appear to be a very effective means of oxygenating small water volumes. Their effect on larger water volumes appears to be less.

...to gain an equivalent amount of oxygen as occurs in small water volumes would likely require air pumps or skimmers far larger than those commonly employed by aquarists.

Powerheads and recirculating pumps do not appear to greatly increase the oxygen...

Using algae in reverse daylight tanks appears to be an effective means of keeping oxygen levels at normoxic levels at night. This effect is pronounced even in tanks and systems that employ protein skimmers and airstones.


Very interesting stuff here. :)

Edited by Whys, 21 March 2012 - 09:46 AM.

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#12
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What do you suppose the lead time is? For example, if I place my display tank and reverse daylight refugium on a 12/12 cycle, will there be an 02 dip at the seams? Conversely, if I place them on a 12/16 cycle, respectively, will there be a bump between the seams, or just continuous saturation?

Is there any benefit to allowing for a few hours of hypoxia each night?

Edited by Whys, 21 March 2012 - 09:58 AM.

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#13
seabass

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All good questions. You might test and experiment with different light cycles and observe the effects.

I can't think of any any benefit to intentionally dropping oxygen levels. Denitrifying bacteria is the only thing I could even speculate that might benefit, but I think that's even a stretch.

I can't really can't remember, but I think that I've read that many macro algae species require day and night cycles. So I'd be inclined to limit the refugium lighting to 12 hours. However, 12 hours seems a bit long for most display tanks. I'm going to refer you to these forums:

Macroalgae & Plants
Discuss the use and care of macroalgae and planted marine tanks.

Biological Filtration
Talk about live rock, refugiums, sand beds, wet/dry filters, etc.


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#14
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Just because this is an interesting conversation I just want to add a point or two.

Although I don't know how much of an effect temperature can have on oxygen in water, I have noted that a lower temperature causes my clownfish to swim at a different area in the tank, closer to the bottom. I lowered the temp from 79 to about 76 and the fish now swims lower. I haven't changed anything else. However this is probably due to coincidence.

Also airstones have a small effect on oxygen in water. What if I ran an airstone in the HOB filter on my tank? Do you think there would be any effect?

#15
Reefmaster1996

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Just because this is an interesting conversation I just want to add a point or two.

Although I don't know how much of an effect temperature can have on oxygen in water, I have noted that a lower temperature causes my clownfish to swim at a different area in the tank, closer to the bottom. I lowered the temp from 79 to about 76 and the fish now swims lower. I haven't changed anything else. However this is probably due to coincidence.

Also airstones have a small effect on oxygen in water. What if I ran an airstone in the HOB filter on my tank? Do you think there would be any effect?

I have tried It and no there is no real difference other than micro bubbles that annoy fish and corals. Also lower salinity and temps do raise oxygen levels, this is a proven fact.

#16
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I thought maybe utilizing the airstone in the filter instead of in the display tank would negate the effects of the micro bubbles since the livestock wouldn't be in direct contact.

I know about the lower temperature increasing oxygen, but just a change of 3 degrees? My clown was always near the surface and over the course of a day he now always swims near the bottom and middle.

#17
Enigma

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There is some really great and though provoking stuff in this thread!

I thought maybe utilizing the airstone in the filter instead of in the display tank would negate the effects of the micro bubbles since the livestock wouldn't be in direct contact.


I would think so as well. The way my HOB works, the airstone would oxygenate the water and then it would be filtered. Any bubbles that were left in the water after passing through the filter (mechanical and chemical components) wouldn't sink to the bottom of the tank when the water re-entered it. It would be impossible for them to wind up on the bottom of the tank. My HOB does create a great deal of turbulence where the water re-enters the tank, so the bubbles would maybe sink a couple of inches.

My one big worry would be the salt creep. I've learned what this is first hand . . . and what a mess.

#18
Whys

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My one big worry would be the salt creep. I've learned what this is first hand . . . and what a mess.


+1. Airstones in saltwater are messy. It isn't even just the salt creep. It's that salt spray. The tiny droplets that pop off in every direction. Coats every nearby surface with a film. In the case of dirty refugium water, salt creep can take on interesting colors and even stain. A glass top is a big help. :)

Edited by Whys, 21 March 2012 - 12:36 PM.

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#19
Enigma

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So, I've completed my test of using an airstone inside my HOB filter.

I feel that it did nothing worthwhile. It didn't help to raise my Ph at all. It didn't create any microbubbles that disturbed the inhabitants of the tank. It did result in a bit of saltcreek on the top of the filter. So, it did nothing positive and one thing negative.

I replace my glass top with egg crate. My Ph is now a solid 8.0, and maybe even a smidge higher.

I have also lowered the temperature of the tank. It now fluctuates between 76 & 78 degrees.