I notice other's don't use air pumps/stones in SW fish only tanks so how do you keep the fish from suffcating?

[4ktvs]

My dad ran saltwater tanks for nearly 20 years before deciding the work wasn't worth it and in his setups he used air pumps with air stones. However the amount of salt that ended up on everything was quite a lot and actually wanted to know how you deal with that before it becomes a mess. I've also read about the losses that happen and know from his experience they happen in the saltwater fish keeping hobby. But it was really sad when the blue spot sting ray passed away after doing well for 3-4 years. He was the best and people that came over thought he was really cool. If I didn't read about how unlucky people have been with them plus the cost I'd really want to give it a shot right off the bat.

Getting back to the subject at hand. I've read some about gas exchange, but nothing has given me a good idea on how to know there is enough going on for the fish in the tank to get by without suffocating. Asking because I am considering setting up my own first saltwater fish only tank. Any insight here would be of help.

 

[brandon429]

homer I like your posts. web point and counter point is how I lived for 23 years straight lol its just a mode.

notice at any given interval, the whole time, my stance is backed by the view of owning a pico reef. a lot can be said about that too / just a mode.

nobody in the big reefs Ive seen are bubbling air it'd cause such a mess nobody would like it.

aquatic-eco.com was amazing though its sad they've been closed about fifteen years now. they were a forty + year company before that, tech engineers and water fluid dynamics statesmen they wrote the good tech blurbs.

 

[Malcontent]

Gas exchange as in
My understanding is that CO2 is readily disolved in seawater or freshwater while O2 isn't in comparison. CO2 is also a heavy gas which congregated more in the lower layers. These lower levels of water need to be brought to the surface and the surface agitated to gas off the CO2. Lots of water movement bring water from below should do this. Oxygen levels have no bearing on CO2 and oxygen not being as soluble is more likely to be deficient. I have an efficent skimmer but also use an Oxydator to keep my Oxygen levels at optimum levels. On the reef esp around breakers oxygen I'd always at saturation point and in fact often exceeds saturation point according to a scientific study I read some years ago. Mixing all water layers seems a good idea to me along with limiting CO2 in the aquarium room.

CO2 is much more soluble than water than O2 but their diffusion coefficients are similar.

I don't think the greater mass of the CO2 molecule would cause it to settle at the bottom. Molecules are so light that even the slightest current would overwhelm the difference between CO2 and O2 mass.

I don't know how effective skimmers are at oxygenation. They could be very effective. There may be some value in creating some kind of external reactor for oxygenation in freshwater tanks.

One other thing I tested was placing a pump (~45 W) at the bottom of the tank with the outlet connected to nothing but aimed upwards. One argument I commonly saw in freshwater forums was that mixing or bringing water from the bottom of the tank to the surface (where gas exchange presumably happens) was critical. The effect on dissolved O2 levels was zero making it the biggest loser compared to the air pump (~3.5 W) and wavemaker (~24 W).

Gas transfer is just not very intuitive. I once thought tap water was probably O2-deficient, tested it, and found it was at 120% saturation. I thought stagnant water might be as well, tested it, and found it was higher than in my tank (with the air stone). I don't rely on intuition anymore when it comes to dissolved gases, I measure instead.

 

[atoll]

CO2 is much more soluble than water than O2 but their diffusion coefficients are similar.

I don't think the greater mass of the CO2 molecule would cause it to settle at the bottom. Molecules are so light that even the slightest current would overwhelm the difference between CO2 and O2 mass.

I don't know how effective skimmers are at oxygenation. They could be very effective. There may be some value in creating some kind of external reactor for oxygenation in freshwater tanks.

One other thing I tested was placing a pump (~45 W) at the bottom of the tank with the outlet connected to nothing but aimed upwards. One argument I commonly saw in freshwater forums was that mixing or bringing water from the bottom of the tank to the surface (where gas exchange presumably happens) was critical. The effect on dissolved O2 levels was zero making it the biggest loser compared to the air pump (~3.5 W) and wavemaker (~24 W).

Gas transfer is just not very intuitive. I once thought tap water was probably O2-deficient, tested it, and found it was at 120% saturation. I thought stagnant water might be as well, tested it, and found it was higher than in my tank (with the air stone). I don't rely on intuition anymore when it comes to dissolved gases, I measure instead.

A skimmer is just as likely to introduce CO2 into the water inbthe case of high levels of CO2 in the same room given CO2s solubility. This has been proven on many occasions and CO2 reduced with a CO2 scrubber. I suspect the amount of O2 a skimmer puts into the water is over exaggerated by many.

 

[fish farmer]

homer I like your posts. web point and counter point is how I lived for 23 years straight lol its just a mode.

notice at any given interval, the whole time, my stance is backed by the view of owning a pico reef. a lot can be said about that too / just a mode.

nobody in the big reefs Ive seen are bubbling air it'd cause such a mess nobody would like it.

aquatic-eco.com was amazing though its sad they've been closed about fifteen years now. they were a forty + year company before that, tech engineers and water fluid dynamics statesmen they wrote the good tech blurbs.

They are still a company, taken over by Pentair, still working with fish but seems more commercial based than before. https://pentairaes.com/

 

[Spieg]

no one uses bubblers in SW. Ok maybe a FOWLR tank, but certainly no bubblers in a reef.

To the contrary, I know may reefers that use a bubbler as a battery backup in the event of a power outage. Not as nice as power heads and skimmer but will keep tank alive in a pinch.

 

[fish farmer]

CO2 is much more soluble than water than O2 but their diffusion coefficients are similar.

I don't think the greater mass of the CO2 molecule would cause it to settle at the bottom. Molecules are so light that even the slightest current would overwhelm the difference between CO2 and O2 mass.

I don't know how effective skimmers are at oxygenation. They could be very effective. There may be some value in creating some kind of external reactor for oxygenation in freshwater tanks.

One other thing I tested was placing a pump (~45 W) at the bottom of the tank with the outlet connected to nothing but aimed upwards. One argument I commonly saw in freshwater forums was that mixing or bringing water from the bottom of the tank to the surface (where gas exchange presumably happens) was critical. The effect on dissolved O2 levels was zero making it the biggest loser compared to the air pump (~3.5 W) and wavemaker (~24 W).

Gas transfer is just not very intuitive. I once thought tap water was probably O2-deficient, tested it, and found it was at 120% saturation. I thought stagnant water might be as well, tested it, and found it was higher than in my tank (with the air stone). I don't rely on intuition anymore when it comes to dissolved gases, I measure instead.

The well water I work with is nitrogen rich, usually total gas is 103%. Coming up from 40 feet you would think this would have very little O2. We get readings of 8 mg/l on raw water, our 100% saturation level is around 11 mg/l when we oxygenate.

 

[4ktvs]

You use poweheads and proper flow. Skimmers also help but that is like their bonus purpose and just poweheads is enough.

Bubblers are never used, only in like a 2 gallon reef.

A stingray probably needs something in the 300g range and set up for their needs and not so much a reef tank. That would be an expensive endeavor for a beginner.

I got a lot more information in this thread than I expected. I'll likely get some airstone as a backup if the power goes out, but won't use it for normal running time.

I've read about what people say a ray needs so I already know the setup wouldn't be cheap.

 

[brandon429]

reef2reef aint playin' around.

 

[dyno]

Wilhelms and Martin 1992 diffused nitrogen gas and air. Diffusing air resulted in much higher dissolved oxygen levels which busted the myth that bubbles only oxygenate via surface agitation 30 years ago:

In 2018, Lee used CFD to further refine the model for bubble plumes and found that >95% of oxygen transfer is bubble transfer:

Numerous studies by the wastewater industry have found that bubble aeration is much more effective than surface aeration:

I've found that a 3.5 W air pump and a 24 W wavemaker positioned to maximize surface agitation were roughly equal in performance, resulting in ~6.3 mg/L dissolved O2 (freshwater tank). Without the air stone, levels dipped as low as 3.9 during the day (which is not healthy) despite the wet/dry filter.

I find your posts in this thread fascinating! I always wondered why large whole sellers and public aquariums still use bubblers in their shark holding/qt facilities. This question has bothered me for years as to whether the bubbles actually do more than just move lower water to the surface, break the surface, and actually allow gas exchange to occur as they travel up though the water.

 

[Galvano]

To prevent evaporation and avoid light fixture corrosion I have a precisely fitting polycarbonate lid covering my tank. Lately low nutrient levels urged me to turn off my skimmer, which is why at night I now run an air pump instead to bring in fresh air, whereas at daytime I expect sufficient oxygen production by photosynthetic organisms (algae / zooxanthellae).