Disolved Oxygen in our Reeftanks - Who else measures it ???

[Subsea]

https://www.reef2reef.com/threads/moving-47-year-old-reef-60-miles-omg.407827/page-11

Paul uses rfug filter and has for 47 years.

@Forsaken77

Why are you focused on anarobic bacteria?

Facultative bacteria vs. Anaerobic Bacteria
I am a supervisor of a wastewater plant. We use nitrification, denitrification in aerobic systems and use anaerobic systems for the destruction of organics.
Phosphate and Nitrate is consumed by facultative bacteria not anaerobic bacteria. Facultative bacteria can switch for a simple explanation to the use of Oxygen from NO3 and PO3 (Nitrate Phosphate) when the Oxygen supply is low starting at usually less than 0.5 mg/L. Ideally less than 0.5 and greater than 0.1. This is called an anoxic zone. Give you an idea of how low this is gold fish need a minimum of 3.0 mg/L Oxygen.
Within the same floc (a clumping growth of bacteria either free floating or growing on a surface) there can be all three bacteria. The outer layer exposed to higher levels of Oxygen allow for the Nitrifiers (Ammonia to Nitrite to Nitrate) The Nitrate reducers live deeper in the floc or rock or sand where there is less Oxygen. We use the same bacterial floc in differing levels of Oxygen to achieve this.
Anaerobic bacteria live in zero Oxygen. They convert organics to water, Carbon Dioxide, and Methane mostly. Hydrogen Sulfide is also a product. You do not want your reef to have anaerobic conditions anywhere. The sulfur dead spots that some people refer to are anaerobic. This happens when a filter media or in this case a sand bed become impacted and diffusion of gas does not take place. Especially true under rocks sitting on sand or worse buried in the sand. A plenum helps moderate the diffusion of gasses through the sand by the osmotic pressure of the levels of dissolved gasses on each side of the sand or filter. (Water under the sand and the water on top of the sand)

So I hope this helps. Facultative bacteria remove Nitrates and Phosphates not anaerobic.

 

[Forsaken77]

https://www.reef2reef.com/threads/moving-47-year-old-reef-60-miles-omg.407827/page-11

Paul uses rfug filter and has for 47 years.

@Forsaken77

Why are you focused on anarobic bacteria?

Facultative bacteria vs. Anaerobic Bacteria
I am a supervisor of a wastewater plant. We use nitrification, denitrification in aerobic systems and use anaerobic systems for the destruction of organics.
Phosphate and Nitrate is consumed by facultative bacteria not anaerobic bacteria. Facultative bacteria can switch for a simple explanation to the use of Oxygen from NO3 and PO3 (Nitrate Phosphate) when the Oxygen supply is low starting at usually less than 0.5 mg/L. Ideally less than 0.5 and greater than 0.1. This is called an anoxic zone. Give you an idea of how low this is gold fish need a minimum of 3.0 mg/L Oxygen.
Within the same floc (a clumping growth of bacteria either free floating or growing on a surface) there can be all three bacteria. The outer layer exposed to higher levels of Oxygen allow for the Nitrifiers (Ammonia to Nitrite to Nitrate) The Nitrate reducers live deeper in the floc or rock or sand where there is less Oxygen. We use the same bacterial floc in differing levels of Oxygen to achieve this.
Anaerobic bacteria live in zero Oxygen. They convert organics to water, Carbon Dioxide, and Methane mostly. Hydrogen Sulfide is also a product. You do not want your reef to have anaerobic conditions anywhere. The sulfur dead spots that some people refer to are anaerobic. This happens when a filter media or in this case a sand bed become impacted and diffusion of gas does not take place. Especially true under rocks sitting on sand or worse buried in the sand. A plenum helps moderate the diffusion of gasses through the sand by the osmotic pressure of the levels of dissolved gasses on each side of the sand or filter. (Water under the sand and the water on top of the sand)

So I hope this helps. Facultative bacteria remove Nitrates and Phosphates not anaerobic.

I know Paul uses it. He's a little old school in the sense. He actually lives 20 mins from me. There's also another old school veteran here that's been using it a while and said it has some benefits, but he wouldn't do it over again if he didn't have to tear the tank down to remove it.

I use the term Anaerobic bacteria in the sense of very low, to almost zero, oxygen. So I guess I'm combining Facultative and Anaerobic, both of which I want. In a 3" fine sand bed that will have some disturbance because I have Wrasses, I would like the Anaerobic to break down residual organics and nitrates to gas off, which will not be trapped. I am hoping to get the bottom layers to process any residual organics and nitrate. The sand sifters eventually disturb those areas.

How does Facultative bacteria come about? It's discretionary. Does it develop in a marine environment? I know water treatment is your thing, but does freshwater treatment equate to saltwater treatment equally?

And you do want Anaerobic bacteria because that is what develops deep inside live rock to process nitrates. Or maybe that's Facultative, but most folks don't use that term in the hobby, or nobody I've heard on a forum really use that term anyway. You're coming at the terminology from an industry standpoint, absolute. As far as most hobbyists go, Anaerobic is considered oxygen-deprived to convert nitrate to nitrogen gas for the most part.

Facultative bacteria can use aerobic properties but gets it's primary energy source anaerobically (the definition). That's why most Nitrate "destroyers" or reactors use slow flow through for anaerobic (or Facultative) bacteria to develop and process nitrates.

I have a ton of different bacteria media to house 10x's more bacteria that's needed, some in low flow areas, yet none have lowered nitrates for me. The bottom layer of my sand will probably not be fully 100% Anaerobic, but Facultative.

My point is the same, I just think we're using different words to describe it. You're using the technical term and I'm using the accepted term, lol , but the goal is the same.

Thanks for pointing that out btw. Because in 20 years I've never heard it called Facultative. Even companies like Seachem call it Anaerobic bacteria to process nitrate. You can just read their description of their products Matrix and de-Nitrate.

 

[Subsea]

https://www.advancedaquarist.com/2002/9/aafeature

Both Bob Goemans & Jean Jaubert discribes the facultative zone in marine substrates to perform denitrification chemistry. In essence, when aerobic bacteria are subjected to reducing oxygen conditions they consume oxygen molecule from nitrate molecule to produce nitrogen free gas as nutrient export. This low oxygen zone is called the facultative zone. According to Bob Goemans, facultative bacteria are 100 fold more efficient at denitrification chemistry than sulfide bacteria in anarobic conditions.

With respect to using anarobic bacteria to destroy organics, I prefer using activated carbon to absorb organic carbon from the water.

 

[Randy Holmes-Farley]

@Randy Holmes-Farley
How is the new job coming?

I got a new job. I joined a new church and volunteered to be the Aggie Horticulture Club. I had already joined the kitchen hospitality crew with the ladies. It is fun to be a volunteer. When it stops being fun, I stop volunteering.

My job is going very well, thanks!

Good luck with the volunteering.

 

[Randy Holmes-Farley]

Thank you! Awesome reading!

You're welcome.

Happy Reefing.

 

[Randy Holmes-Farley]

Anyone actually have an issue of too low DO? Considering our tanks are in Eq with the surrounding atmosphere (which is never hypoxic or we would be dead also) unless they are sealed off completely or undergoing a massive bacterial bloom it seems like it may just be something irrelevant to measure. Also we do have a lot of algae in a small enclosed environment so that will always help.

I think that is something that is hard to know. Since it is expensive to measure well, and the evidence is not clear that it makes a big difference in most reef taniks, I think it is best suited for folks who like to experiment. Sort of like dosing individual trace elements.

But it might well be important. Folks who increase flow or add skimmers and claim to see benefits, is that really from the flow or skimming, or from increased aeration?

 

[mcarroll]

A few links...
4. BASIC PRINCIPLES OF THE DESIGN OF FISH POND AERATORS
This one has the details and formulas that a couple folks might be interested in.


Low Oxygen and Pond Aeration

Oxygen Depletion

A number of conditions may develop which result in oxygen depletion, DO at levels insufficient (less than 3 mg/l) to support aquatic life (e.g. fish).

SRAC 0453: Recirculating Aquaculture Tank Production Systems: A Review of Current Design Practice

Aeration (oxygen addition)

The aeration process deals with the transfer of oxygen into the water. Oxygen is a relatively rare component in in water with 10 ppm being considered a high concentra- tion. Most warm water recirculating systems operate with an oxygen level in the range of 5 to 6 parts per million; whereas, cooler recirculating systems can operate above 8 parts per million. Both the fish and bacteria rapidly con- sume oxygen. Under high loads, the RAS aeration system must be capable of replacing all oxygen in the system every 20 to 30 minutes at peak feeding rates.

Carbon Dioxide Removal

Degassing is similar to aeration although carbon dioxide is a highly soluble gas, whereas, oxygen is a poorly soluble gas. The earth’s atmosphere is over 20 percent oxygen, yet contains only about 0.04 percent carbon dioxide. Under normal conditions, surface water will contain about 0.5 parts per million of carbon dioxide. In a poorly designed RAS, the respiration activities of both fish and bacteria produce a tremendous amount of carbon dioxide, elevating water levels to the 50 to 100 parts per million range. The high carbon dioxide level lowers pH and causes nitrifying bacteria to cease to function; resulting in a rise in nitrite or ammonia levels. Carbon dioxide is usually removed by blown air or by unpressurized packed columns.

These aquaculture guides are packed with great info, so check em out....here's another quote from this one:

Tanks

Sizing of fish tanks is based upon the density of fish, the primary controller of system stability. The fish density also ultimately controls the feed application rate. A very low fish density (<1/8 pound of fish per gallon or <15 kg/ m3) is commonly used for broodstock and display appli- cations where the stock is considered extremely valuable. [...] Densities of about 1 pound per gallon (120 kg/m3) of water can be achieved, but, often display unstable water quality and are thus more prone to disease and growth issues.

By this guide, we'd want less than 15.6 pounds of fish in a 125 gallon tank for ideal heath and maximized success.

A quick google says that a Hippo Tang might weigh 1.3 pounds.

If all your fish were Hippo size, that would mean less than 12 (grown) fish in a 125 gallon tank.

But it also suggests that one might attain densities up to 96 fish in a 125 gallon. But expect trouble.

It says in another section (click and read!) that half a pound per gallon is an "accepted" stocking rate....something like 48 fish in a 125 gallon.

Those folks (aquaculture) have an acceptable loss rate and no prized specimens. (just to name two differences with us)

Folks like us that stock less than 1/8 of a pound of fish per gallon will overall have an easier time of things. Less is more.

To me this seems like a realistic set of ratios.

A great read!

 

[norfolkgarden]

Strange question.

If surface agitation is the primary transferance area during emergency procedures with power loss and a battery backup air stone,
is a weighted open airline with heavy splashing better then a lime wood air bubbler with a column of tiny fine bubbles?

Is the difference small enough to not really matter?

Thanks!

 

[mcarroll]

Strange question.

If surface agitation is the primary transferance area during emergency procedures with power loss and a battery backup air stone,
is a weighted open airline with heavy splashing better then a lime wood air bubbler with a column of tiny fine bubbles?

Is the difference small enough to not really matter?

Thanks!

5.1 Bubble Aeration

Has some answers, but doesn't answer directly.

Finer is better, but "enough" is a different question.

 

[rkpetersen]

I've measured DO at times years ago and more recently with the Lamotte DO test kit, on a few different tanks, but have never seen a number higher than 6.8 ppm with it, or roughly 100% saturation. It's a relatively high quality kit that's been in use for decades, and that also allows for a rough assessment of the water source's biological oxygen demand (by collecting a second sample.)

OP, I picked up one of the meters that you're using in the first post (thanks for pointing me to it.) After setup and calibration, including setting the Salt percentage to 4% (no option for 3.5%), I'm getting measurements of 7.7-7.8 ppm dissolved oxygen midday in the DT. That's a considerable difference from the Lamotte test, and suggests the presence of substantial supersaturation (presumably due primarily to photosynthesis, as in nature.) Clearly, I'd prefer to believe this device's results over the Lamotte test results. But 113% saturation does seem improbably high to me, though, especially considering that my overflow is silent. Also - a 10g quarantine tank, currently empty of fish, with a cheap hob filter and small Tunze in-tank skimmer, lit by a few weak LEDs, also shows a DO of 7.7 ppm with the meter.

I was also curious as to whether you've experimented with the salt or altitude settings on the meter? This device resets all the settings to default (freshwater at sea level) when you turn it off, so you have to reconfigure the settings for saltwater (and altitude) every time you turn it on. Although whether the device is set for seawater or not seems to make relatively little difference, no more than 0.1 ppm in the reading.

 

[mcarroll]

@rkpetersen When you can, get some readings throughout a day for comparison.

If it IS diurnal variation (supersaturation due to photosynthesis) causing it to be so high, then that should be clear within a few samples. E.g. two hours before lights out, at lights-out, and two hours after lights-out.

If there's a big shift in O2 that follows the shift to (or from) respiration, you should see it. Even if the absolute number on the display is incorrect, the trend should be pretty clear. (Then if you can make the number pretty correct that would help a lot too. )

I think if there IS a significant day/night trend, I'm sure you'll want to do something about it....again, regardless of numbers, since the swing itself implies a lack of mixing.

Has anyone tried the Salifert DO kit?

 

[mcarroll]

BTW, this is a perfectly nerdy thread – keep it going!

 

[rkpetersen]

@rkpetersen When you can, get some readings throughout a day for comparison.

If it IS diurnal variation (supersaturation due to photosynthesis) causing it to be so high, then that should be clear within a few samples. E.g. two hours before lights out, at lights-out, and two hours after lights-out.

If there's a big shift in O2 that follows the shift to (or from) respiration, you should see it. Even if the absolute number on the display is incorrect, the trend should be pretty clear. (Then if you can make the number pretty correct that would help a lot too. )

I think if there IS a significant day/night trend, I'm sure you'll want to do something about it....again, regardless of numbers, since the swing itself implies a lack of mixing.

Has anyone tried the Salifert DO kit?

Thanks, I'm actually planning on taking some numbers later today and tonight, and see what I get. Regarding whether I'll want to do something if there's a consistent DO dip at night. To some degree it depends on how much of a dip occurs. A nighttime drop is actually the normal situation on coral reefs, as also shown in the discussion of the third part of that Borneman article series. I already run a fuge on a reverse lighting cycle, although it is rather small and I think unlikely to fully compensate for absence of photosynthetic activity at night in the DT.

In any case, it still won't answer whether the meter or the test kit is more accurate. The meter calibrates to atmospheric O2, but how well this single-point calibration works at the level of DO measurements in saltwater, I have no idea.

I have tried the Salifert DO test kit; it is nothing like the Lamotte kit, and of too low accuracy and precision to be of use, imo.

 

[Subsea]

Strange question.

If surface agitation is the primary transferance area during emergency procedures with power loss and a battery backup air stone,
is a weighted open airline with heavy splashing better then a lime wood air bubbler with a column of tiny fine bubbles?

Is the difference small enough to not really matter?

Thanks!

Large bubbles move more water in the vertical plane. It depends on surface agitation and imo, you will get more surface agitation with larger bubbles. On the other hand, smaller bubbles transfer more oxygen per air volume than large bubbles, but move less water to effect surface agitation.

 

[Mortie31]

I've measured DO at times years ago and more recently with the Lamotte DO test kit, on a few different tanks, but have never seen a number higher than 6.8 ppm with it, or roughly 100% saturation. It's a relatively high quality kit that's been in use for decades, and that also allows for a rough assessment of the water source's biological oxygen demand (by collecting a second sample.)

OP, I picked up one of the meters that you're using in the first post (thanks for pointing me to it.) After setup and calibration, including setting the Salt percentage to 4% (no option for 3.5%), I'm getting measurements of 7.7-7.8 ppm dissolved oxygen midday in the DT. That's a considerable difference from the Lamotte test, and suggests the presence of substantial supersaturation (presumably due primarily to photosynthesis, as in nature.) Clearly, I'd prefer to believe this device's results over the Lamotte test results. But 113% saturation does seem improbably high to me, though, especially considering that my overflow is silent. Also - a 10g quarantine tank, currently empty of fish, with a cheap hob filter and small Tunze in-tank skimmer, lit by a few weak LEDs, also shows a DO of 7.7 ppm with the meter.

I was also curious as to whether you've experimented with the salt or altitude settings on the meter? This device resets all the settings to default (freshwater at sea level) when you turn it off, so you have to reconfigure the settings for saltwater (and altitude) every time you turn it on. Although whether the device is set for seawater or not seems to make relatively little difference, no more than 0.1 ppm in the reading.

The salinity has a large impact on DO levels, can the device not be calibrated more accurately, the Boremen articles attached by Randy got brought this in some detail, your levels of 113% I see in my system but I have to increase surface disturbance more to achieve it.

 

[Mortie31]

Thanks, I'm actually planning on taking some numbers later today and tonight, and see what I get. Regarding whether I'll want to do something if there's a consistent DO dip at night. To some degree it depends on how much of a dip occurs. A nighttime drop is actually the normal situation on coral reefs, as also shown in the discussion of the third part of that Borneman article series. I already run a fuge on a reverse lighting cycle, although it is rather small and I think unlikely to fully compensate for absence of photosynthetic activity at night in the DT.

In any case, it still won't answer whether the meter or the test kit is more accurate. The meter calibrates to atmospheric O2, but how well this single-point calibration works at the level of DO measurements in saltwater, I have no idea.

I have tried the Salifert DO test kit; it is nothing like the Lamotte kit, and of too low accuracy and precision to be of use, imo.

I see a very predictable diurnal swing in my system, I have no fuge at all.

 

[Subsea]

I see a very predictable diurnal swing in my system, I have no fuge at all.

Your display is gorgeous and full of photosynthetic corals that all consume oxygen and give off carbon dioxide during lights out. During lights out, pH drops which I consider to be good. Reefs in the wild fluctuate from 8.2 - 7.8. I use those pH swings to dissolve aroggonite to produce calcium & magnesium for alkalinity management and trace mineral addition.

Have you had unexplained fish deaths? Do you have problems with pH swings? Looking at your display, I see no low oxygen evidence. You have a large oxygen demand that should have some type of ups backup system.

Your tank is gorgeous. Kudos to you.

 

[Mortie31]

Your display is gorgeous and full of photosynthetic corals that all consume oxygen and give off carbon dioxide during lights out. During lights out, pH drops which I consider to be good. Reefs in the wild fluctuate from 8.2 - 7.8. I use those pH swings to dissolve aroggonite to produce calcium & magnesium for alkalinity management and trace mineral addition.

Have you had unexplained fish deaths? Do you have problems with pH swings? Looking at your display, I see no low oxygen evidence. You have a large oxygen demand that should have some type of ups backup system.

Your tank is gorgeous. Kudos to you.

Thankyou very much, I have had no issues at all, no fish deaths, corals are growing well, my ph is generally from 8 - 8.3 during the diurnal swing, so about normal I think, I have actually just seen it drop slightly to 7.9 due to my shutting doors and windows as the outside temp starts to drop, but this is entirely normal for my tank. From what I have seen a DO swing of 80% to 100% doesn’t seem to have any noticeable effect at all, I do have 2 battery backups and a UPS as well, and a gene in the garage just in case. I’m mainly just observing DO and making changes to see how different setups affect it, not scientific but just my observations. When I get time I’ll try turning the skimmer off and observing levels to see just how they affect DO. In the articles Randy posted the DO levels in the various test tanks seem to be in the same ball park as my findings, so not worried at all.

 

[rkpetersen]

I see a very predictable diurnal swing in my system, I have no fuge at all.

Right, I think this is fairly normal, for the reason mentioned by Subsea and for much the same reason that there's normally a diurnal pH variation. I took several readings in the evening and during the night with the new meter, and the DO measurement fell to a minimum of 7.2 ppm in both DT and sump at 6 AM. I'm honestly surprised it stayed that high given that it would still represent supersaturation if it's an accurate measurement, and as I mentioned above, I'd be surprised if my tiny fuge can pump out enough O2 to maintain that condition in the absence of photosynthesis in the DT as well.

 

[rkpetersen]

The salinity has a large impact on DO levels, can the device not be calibrated more accurately, the Boremen articles attached by Randy got brought this in some detail, your levels of 113% I see in my system but I have to increase surface disturbance more to achieve it.

The 'Salt' adjustment function on this meter is from 1 to 39 percent salinity, in 1% increments. Seawater is 3.5% salt (and for comparison, human blood serum is 0.9%.) This adjustment should just affect the dissolved oxygen measurement slightly. That's not the same consideration as the much lower solubility of oxygen in saltwater compared to freshwater. This meter doesn't need that info because it doesn't report a saturation percentage; that number however is easily calculated from the measurement obtained and comparison to a solubility table.