Oxygenation When Going Skimmerless

[fryman]

There is a thread where someone actually bought a dissolved oxygen meter and measured DO under various conditions.
https://www.reef2reef.com/threads/disolved-oxygen-in-our-reeftanks-who-else-measures-it.460332/
Sometimes the skimmer seemed to increase DO slightly, sometimes it seemed to depress DO slightly. The impact was always relatively modest.

I try to make data-driven decisions whenever possible. I'm still not seeing any evidence that a skimmer is necessary or even relevant to maintaining good dissolved O2 level. There are other benefits running a skimmer, no doubt. But take away the skimmer cup and I have doubts.

 

[Randy Holmes-Farley Verified Community Expert]

I try to make data-driven decisions whenever possible. I'm still not seeing any evidence that a skimmer is necessary or even relevant to maintaining good dissolved O2 level. There are other benefits running a skimmer, no doubt. But take away the skimmer cup and I have doubts.

Data driven is perfect. Here's some data showing the benefit of a skimmer on O2, and that even with skimming, saturation with O2 is not always complete:

http://reefkeeping.com/issues/2005-08/eb/index.php
Compare figures 1 and 2 for an extreme case of a benefit from a skimmer, with my highlighting:

"The ten-gallon tank containing clownfish has been set up as an unskimmed system with what I consider to be an average stocking density of organisms for a tank of its size. I had assumed (wrongfully) that oxygen was maintained at high levels through the use of two powerheads that agitated the water's surface. However, once the lights went out and photosynthesis stopped, oxygen levels dropped quickly from a high of 78.7% of saturation to a hypoxic low of 16% of saturation. The levels were apparently low enough that each night, the clownfish would leave their anemone and adopt a position just under the water's surface directly above a powerhead. Out of concern, I then monitored the changes in oxygen levels at night using an airstone. Oxygen rose quickly and dramatically. At that point, I added a skimmer to the tank, with the result that oxygen is now maintained at much higher levels, ranging from a high of 130% of saturation to a low of 81.2% of saturation. "

And Eric's conclusion:

"Airstones and skimmers appear to be a very effective means of oxygenating small water volumes."

 

[fryman]

Data driven is perfect. Here's some data showing the benefit of a skimmer on O2, and that even with skimming, saturation with O2 is not always complete:

http://reefkeeping.com/issues/2005-08/eb/index.php

Darn you, Randy, now I want to buy a DO meter. My wife is going to be just thrilled, I already spend too much on this hobby. I intend to blame you.

I have a 15gal unskimmed tank that I assumed (like the author of that article) was fine with just surface agitation. Maybe I will add an airstone. I think on a timer so it just comes on at night.

Ty for the info

 

[Joeg]

We'll, I'm going to disappoint anyone looking for hard data on this but after 3 days without the skimmer running I saw PO4 go from .04 to .13 but NO3 never budged from 10ppm. ALK and CA consumption also remained steady at 9.2 and 410. The phosphate increase may have been because I pruned a little bit of algae from the small fijicube fuge that hangs off the sump but I tend to think it had more to do with the skimmer being turned off.

I flipped the skimmer back on this morning because to me it looked like there was a tinge of brown on the sand in the back corner. Weeks ago I had finally conquered dinos and a little bit of gha so the last thing I wanted to do was provide a foothold for a return because they tank is really looking good now. For anyone interested I can't pinpoint what I did to get rid of the algae because in the least scientific way possible I made several changes a about a month ago that included dosing phyto daily plus Microbacter 7 and NoPox weekly....I also bumped the temp up to 80 around the same time so some combination of those or all of them together really clobbered my algae problem within 10 days or so.

I think I'm just going to live with the occasional frustration of the skimmer overflowing once in a while. I like the idea of a larger fuge and if I had a basement sump there wouldn't even be a discussion but the area under the stand is full so unless everything goes sideways at some point I think what I have going on right now works for a softie/lps tank.

I guess the saying goes that you shouldn't mess with something that's working fine....so that's my plan.....except for the 2 additional lights that just shipped which will really make my lighting array worthy of a Frankenstein award :)

Thanks again for everyones input. It was good to get some opinions and the links that everyone posted were some good reading to better understand what's going on.

 

[zalick]

Data driven is perfect. Here's some data showing the benefit of a skimmer on O2, and that even with skimming, saturation with O2 is not always complete:

http://reefkeeping.com/issues/2005-08/eb/index.php
Compare figures 1 and 2 for an extreme case of a benefit from a skimmer, with my highlighting:

"The ten-gallon tank containing clownfish has been set up as an unskimmed system with what I consider to be an average stocking density of organisms for a tank of its size. I had assumed (wrongfully) that oxygen was maintained at high levels through the use of two powerheads that agitated the water's surface. However, once the lights went out and photosynthesis stopped, oxygen levels dropped quickly from a high of 78.7% of saturation to a hypoxic low of 16% of saturation. The levels were apparently low enough that each night, the clownfish would leave their anemone and adopt a position just under the water's surface directly above a powerhead. Out of concern, I then monitored the changes in oxygen levels at night using an airstone. Oxygen rose quickly and dramatically. At that point, I added a skimmer to the tank, with the result that oxygen is now maintained at much higher levels, ranging from a high of 130% of saturation to a low of 81.2% of saturation. "

And Eric's conclusion:

"Airstones and skimmers appear to be a very effective means of oxygenating small water volumes."

Thanks for sharing the link.

Interesting that Eric noted on his 75g puffer tank and his 600g reef that "[a skimmer's] effect on larger water volumes appears to be less. While the effect may be relative, the larger tanks and systems described here utilized powerful skimming or air pumps, and 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"

And he specifically noted that in his 600g system "In this system, it does not appear that skimming or the Tunze Stream powerheads impact oxygen levels to any great degree"

 

[beginner_reefer]

Not enough. 1hr isn't enough time to build up the foam head. Run it 24/7.

Ok. Just

Not enough. 1hr isn't enough time to build up the foam head. Run it 24/7.

Wasn't sure if that was bad for it since the tank is so new.

 

[beginner_reefer]

I would always run a simmer 24/7 for aeration, even if you didn't want to collect skimmate for some reason.

Thank you! Will take it off of the timer as soon as I get home from work today.

 

[Randy Holmes-Farley Verified Community Expert]

Thanks for sharing the link.

Interesting that Eric noted on his 75g puffer tank and his 600g reef that "[a skimmer's] effect on larger water volumes appears to be less. While the effect may be relative, the larger tanks and systems described here utilized powerful skimming or air pumps, and 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"

And he specifically noted that in his 600g system "In this system, it does not appear that skimming or the Tunze Stream powerheads impact oxygen levels to any great degree"

I suspect that the scale up in skimmer size may be suitable for the "skimming" needs, but that it doesn't scale up the absolute amount aeration by 60 fold between his 600 gallon tank and his 10 gallon tank.

Figure 5 in this previous article of his has a nice comparison of a skimmer, airstone, and powerhead on the same small tank:

http://www.reefkeeping.com/issues/2005-07/eb/index.php

 

[Powertool-2010]

I suspect that the scale up in skimmer size may be suitable for the "skimming" needs, but that it doesn't scale up the absolute amount aeration by 60 fold between his 600 gallon tank and his 10 gallon tank.

Figure 5 in this previous article of his has a nice comparison of a skimmer, airstone, and powerhead on the same small tank:

http://www.reefkeeping.com/issues/2005-07/eb/index.php

My guess is that as the system gets larger it also gets more complex with more robust interactions between the plants, corals, fish, external environmental factors,and Oxygen and CO2 cycles, as well as the larger volume acting as a buffer, to stabilize the system from sudden external changes. I frustratingly can't seem to follow the articles link right now for some reason, so I'm really just speculating in the dark, and some of those ideas might even be addressed in said article.
As far as the initial question. I would think that if you kept the refugium lit with a reverse photoperiod it would benefit the system in a similar way as the daytime parameters of the 10g tank talked about by people referencing the article. Anecdotally I have a refugium on a reverse photoperiod and although it does benefit (based on ph which is inversely equivalent to co2 levels which itself is inversely proportional to the oxygen that is produced from photosynthesis) I still get large swings in my main display. I think this is due to gas off going over sump baffles as well as gas off from the return which ejects planarly across the top of the tank also our house is more filled with CO2 producers during the night as well. All in all I end up with a 0.1 average Ph fluctuation during the course of a day. If I remember right. Without the refugium it would drop another. 05 ph or more.

 

[Adamantium]

My skimmer runs without the collection cup, just for oxygenation. I realized a while back that my tanks looks better when it doesn’t run. Maybe because my refugium and coral at this point are uptaking enough nitrate out the water to keep a stable .02. Just a little pink on the salifert.

I don’t think it’s possible to measure .02 on the Salifert?

 

[blasterman]

Anybody here ever have terrariums. You know....the ones that are enclosed and pretty much airtight? Wow...plants grow in them...without much air transfer.

No skimmer in those terrariums. No one worries about O2 levels.

Ever see a skimmer on a heavily planted FW tank? Nope. Far, far more planted biomass on those tanks than a reef tank.

Plants don't care much about O2 because they dont have lungs. They are more concerned about moving 02 away from their internal tissues because its poison and can inhibit growth.

Xoonthalae algae in corals are plants. Anybody have issues understanding that? Why does high ammonia levels kill fish but not corals. Because corals, which host symbiotic algae, which are plants, dont burn O2. O2 has to be migrated out of plant tissues because it can inhibit photosynthesis. Plant....mammal...invertebrate...covered in grade school science glass...or was. Not sure anymore. Same with the actual O2 content of air.

Anyways, the amount of gas transfer accomplished by skimmers and airstones isn't as much as you think which is why fisheries are using high tech oxygen ingestion systems instead of airstones.

The gas composition in your tank otherwise can only be equalized to what it is externally.

Running a skimmer with outside air to reduce CO2 simply means your room air sucks . You aren't increasing the oxygen level in your tank. You are bypassing your crappy inside air and just normalizing your tank gas levels with outside air because building codes are obsessed with insulation. If your room air gas levels were the same as outside you wouldn't need to plumb your skimmer to the outside. Wow
..common sense...what a thing.

Not picking on skimmers....but the myth that corals need gas levels like , uh, mammals is a bit silly. Kind of like LEDs can grow coral.

 

[N.Sreefer]

Easy solution to up gas exchange cut the pipe going from the overflow to the sump short a foot or two and have it fall over a sponge or pot scrubbies. Could also size up the pipe diameter of the overflow so the water is mixing with air in the pipes.

 

[ReefHomieJon]

I don’t think it’s possible to measure .02 on the Salifert?

I meant .2
I Blame it on my what was in my cup that day