Oxygenation question : do I really need a protein skimmer?

[Raazka]

Hi all,

I’ve recently had some trouble with my new clownfish couple and it’s now seeded some anxiety over if I’m correctly receiving oxygen in my tank water.

How to know if my fish are having trouble getting oxygen? Only my clowns (which have been in the tank for a week now) have been breathing fast and acting weird in the last two days, all other fish that have been in the tank for multiple months are acting like usual and appear fine.

I’ve always just had two powerheads pointed at the surface (every spot of the water surface is moving), an HOB filter and a surface skimmer and it’s been working really well. Is this actually enough or should I replace the surface skimmer with a protein skimmer?

TIA!

 

[EeyoreIsMySpiritAnimal]

Sounds like enough surface agitation to me, especially the HOB filter.

 

[Fish Fan]

Are the Clowns just breathing rapidly, or do they seem like they're gasping at the surface?

Gasping at the surface may be a sign of low oxygen.

Rapid breathing is a symptom of Brooklynella, which Clowns are particularly susceptible to, as well as Velvet and others. So this could be a disease and not low oxygen.

 

[Randy Holmes-Farley]

Skimmers do help oxygenation, although I do not know if that is your issue. Complete gas exchange can be harder than many people expect, which is evident in the day night pH swing in nearly all reef tanks regardless of how well aerated a reef may think they are.

Perfectly aerated seawater will only change in pH if the CO2 level in the air changes, and in most cases, CO2 is not rising at night in the vicinity of your reef tank. It is being generated in the tank and is not exchanged out.

That doesn't prove anything about O2 problems, except that reef tanks are nearly always incomplete in gas exchange.

 

[Raazka]

Sounds like enough surface agitation to me, especially the HOB filter.

Thank you, I’ve been told that I was missing agitation and couldn’t get it off my mind

 

[Raazka]

Are the Clowns just breathing rapidly, or do they seem like they're gasping at the surface?

Gasping at the surface may be a sign of low oxygen.

Rapid breathing is a symptom of Brooklynella, which Clowns are particularly susceptible to, as well as Velvet and others. So this could be a disease and not low oxygen.

Breathing rapidly but not gasping for air. First it was only the female, but as of today the male is also breathing slightly faster.

These clowns have been where I work for at least 2-3 weeks (LFS), they never showed any signs of illnesses and got along so I took them home. Completely fine and very active for the first week but yesterday I found the female laying on some macro-algae leaves breathing rapidly and not moving. The male was acting as usual. After an hour, she started swimming again but was still breathing fast. Today, same thing, both are swimming in macro-algae, female is breathing faster than the male. No signs of any diseases or injuries.

I have no idea why they’re suddenly acting like this.

 

[Fish Fan]

Breathing rapidly but not gasping for air. First it was only the female, but as of today the male is also breathing slightly faster.

These clowns have been where I work for at least 2-3 weeks (LFS), they never showed any signs of illnesses and got along so I took them home. Completely fine and very active for the first week but yesterday I found the female laying on some macro-algae leaves breathing rapidly and not moving. The male was acting as usual. After an hour, she started swimming again but was still breathing fast. Today, same thing, both are swimming in macro-algae, female is breathing faster than the male. No signs of any diseases or injuries.

I have no idea why they’re suddenly acting like this.

I'm not an expert, but this sounds more like an illness to me. Let's see if someone more knowledgeable is around to give you more solid advice here.

#fishmedics

 

[Raazka]

Skimmers do help oxygenation, although I do not know if that is your issue. Complete gas exchange can be harder than many people expect, which is evident in the day night pH swing in nearly all reef tanks regardless of how well aerated a reef may think they are.

Perfectly aerated seawater will only change in pH if the CO2 level in the air changes, and in most cases, CO2 is not rising at night in the vicinity of your reef tank. It is being generated in the tank and is not exchanged out.

That doesn't prove anything about O2 problems, except that reef tanks are nearly always incomplete in gas exchange.

Thank you for the explanation, then do you think what’s happening to my clowns could be pH related?

 

[Randy Holmes-Farley]

Thank you for the explanation, then do you think what’s happening to my clowns could be pH related?

No. I was using pH as evidence that gas exchange is hard. I agree with folks thinking it is most likely disease related, but I’m not an expert on diseases.

 

[Raazka]

No. I was using pH as evidence that gas exchange is hard. I agree with folks thinking it is most likely disease related, but I’m not an expert on diseases.

Alrighty thank you, male is now acting fine and swimming around the tank. Female is still hiding and breathing fast but she’s responding to her surroundings.

I have no clue what happening lol

 

[Fish Fan]

Could you post a couple pics or a clear, short video showing the fish the and odd behavior? Please use the “whitest” light you have, turn off your blues if you can. This will help others better help you figure out what’s going on.

 

[Raazka]

Could you post a couple pics or a clear, short video showing the fish the and odd behavior? Please use the “whitest” light you have, turn off your blues if you can. This will help others better help you figure out what’s going on.

I’m unable to add a video or photo at the moment because she’s been hiding behind rocks that make it impossible for my camera to focus on her.

She’s moved from her original spot from yesterday and is now in another macro-algae batch. She’s staying at the exact same spot, swimming in place normally (no jerky movement, just normal but slow swimming) and opening her mouth rapidly to breathe, about 3-4 mouth openings a second. She didn’t come out to eat when I dropped in food. She has no mucus coming off, no white scrapes or spots, no ich spots, no physical injuries.

Male has stopped breathing fast, is now swimming around the tank normally and has eaten. He’s also physically unscathed. All other fish and inverts are acting like usual.

I’m starting to think that she may have scraped her gills or gotten some kind of trauma.

 

[Fish Fan]

Well if she comes out and you can get a video, I think that would be helpful. I’m sure one of the R2R #fishmedic crew will see this soon. Sorry I can’t be more help here, but I don’t want to give you wrong advise.

 

[Miami Reef]

Skimmers do help oxygenation, although I do not know if that is your issue. Complete gas exchange can be harder than many people expect, which is evident in the day night pH swing in nearly all reef tanks regardless of how well aerated a reef may think they are.

Perfectly aerated seawater will only change in pH if the CO2 level in the air changes, and in most cases, CO2 is not rising at night in the vicinity of your reef tank. It is being generated in the tank and is not exchanged out.

That doesn't prove anything about O2 problems, except that reef tanks are nearly always incomplete in gas exchange.

I have a fish quarantine tank. Do you think an airstone “injects” fresh air and oxygen better than a powerhead pointed at the surface?

 

[Randy Holmes-Farley]

I have a fish quarantine tank. Do you think an airstone “injects” fresh air and oxygen better than a powerhead pointed at the surface?

I think it depends on the details. The key is how much surface area is exchanged with fresh air and water per unit of time.

 

[Fish Fan]

I have a fish quarantine tank. Do you think an airstone “injects” fresh air and oxygen better than a powerhead pointed at the surface?

If it helps to think of it this way, my understanding is that an airstone doesn't really inject or drive any gas into the water. It makes bubbles that float upward, causing water movement. The bubbles burst at the surface, causing surface disruption, and this surface agitation is where the gases are exchanged. So pretty much the same mechanism as a powerhead.

Now, I don't know for sure, but I am tempted to believe that a good air stone and pump may be better at gas exchange than a powerhead pointed to the surface because I *believe* it's doing more to cause surface disruption, just from observation and a few "probably's" concluded :)

EDIT: Many of those original poweheads that sat on top of the uplift tube on an under gravel filter often had a venturi tube/valve that allowed you to make A LOT of little bubbles with the water movement. Perhaps that setup may be the most efficient at gas exchange, kind of the best of both worlds. Speculation, of course.

 

[Miami Reef]

Thanks, guys! I appreciate the info!

 

[Malcontent]

I have a fish quarantine tank. Do you think an airstone “injects” fresh air and oxygen better than a powerhead pointed at the surface?

Yes, air stones and air pumps use ~7 times less power to achieve the same dissolved oxygen levels. This is consistent with experiments done by the wastewater treatment industry which switched from surface aeration to bubble aeration decades ago.

Air stones don't seem to work very well in very shallow water (3-4").

If it helps to think of it this way, my understanding is that an airstone doesn't really inject or drive any gas into the water. It makes bubbles that float upward, causing water movement. The bubbles burst at the surface, causing surface disruption, and this surface agitation is where the gases are exchanged. So pretty much the same mechanism as a powerhead.

This is a very common misconception. There have been a number of studies done to separate the oxygen transfer of a bubble plume into its bubble transfer and surface transfer components. The earliest I'm aware of (from 1992) alternatingly diffused nitrogen gas and air and estimated that 2/3rds of the total oxygen transfer is bubble transfer.

More recent studies done at bench scale (closer in size to aquariums) found it to be even higher (89-97%).

 

[Randy Holmes-Farley]

I’ve never understood why folks discount gas transfer inside bubbles. They do add surface area of transfer, and are also under pressure, forcing more O2 into the water.

 

[Subsea]

Yes, air stones and air pumps use ~7 times less power to achieve the same dissolved oxygen levels. This is consistent with experiments done by the wastewater treatment industry which switched from surface aeration to bubble aeration decades ago.

Air stones don't seem to work very well in very shallow water (3-4").



This is a very common misconception. There have been a number of studies done to separate the oxygen transfer of a bubble plume into its bubble transfer and surface transfer components. The earliest I'm aware of (from 1992) alternatingly diffused nitrogen gas and air and estimated that 2/3rds of the total oxygen transfer is bubble transfer.

More recent studies done at bench scale (closer in size to aquariums) found it to be even higher (89-97%).

As a former municipal waste water superintendent, I second the efficacy of air bubblers. Also, AquaCulture Ranch, as a mariculture facility, the economy of scale using air movers is unparalleled.