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

[Mortie31]

From what I have observed in my very crude experimenting, the amount of surface agitation is crucial to O2 levels, if I point a powerhead at a steeper angle and create masses of agitation the levels increase quickly, however practicalities of noise, splashing etc have to be factored in for the net gain, and does this gain actually benefit anything?? Which is why I’m trying to find the balance between agitation, water circulation and O2 levels. One other thing I observed was if I allow the water level in my overflow to drop so the overflowing water has a 18” drop onto a shallow pool in the bottom of the overflow which is then very turbulent the O2 levels increase dramatically, but again this is incredible noisy and not practical for me.

 

[Subsea]

From what I have observed in my very crude experimenting, the amount of surface agitation is crucial to O2 levels, if I point a powerhead at a steeper angle and create masses of agitation the levels increase quickly, however practicalities of noise, splashing etc have to be factored in for the net gain, and does this gain actually benefit anything?? Which is why I’m trying to find the balance between agitation, water circulation and O2 levels. One other thing I observed was if I allow the water level in my overflow to drop so the overflowing water has a 18” drop onto a shallow pool in the bottom of the overflow which is then very turbulent the O2 levels increase dramatically, but again this is incredible noisy and not practical for me.

You are correct about surface agitation increasing gas exchange. Surface tension impedes gas exchange and surface agitation decreases surface tension thereby increasing gas exchange. Gas exchange is a two way street. This includes oxygen as well. Water will only saturate a certain amount of oxygen depending mostly on temperature and partial pressure of oxygen in air. During photosynthesis, excess oxygen produced in system water leaves the water and goes to the air at the same time that carbon dioxide gas is entering the water to feed bicarbonate alkalinity to produce glucose during photosynthesis.

 

[Forsaken77]

You mentioned removing your sandbed. Considering bacteria consumption of oxygen 24/7, do you expect oxygen concentration to increase in your system after removing bacteria in the sandbed?

https://www.reef2reef.com/threads/sochting-oxidator-advice-needed-please.283145/

I would imagine that removing the sand bed wouldn't have a direct result in aerating the water. The same principle applies to having 10 Marine Pure balls vs having 100. Bacteria will only colonize to the degree it can be supported.

Removing the bed will cause the bacteria to colonize elsewhere, given the medium to colonize. There will always be a balance with aerobic bacteria to the amount available food source it can consume.

I've already seen that oxygenator that you linked to before. Unfortunately it's not easy to come by and the catalyst (wish I knew what it was) is always out of stock. But appreciate the gesture nonetheless .

 

[Randy Holmes-Farley]

You are correct about surface agitation increasing gas exchange. Surface tension impedes gas exchange and surface agitation decreases surface tension thereby increasing gas exchange. Gas exchange is a two way street. This includes oxygen as well. Water will only saturate a certain amount of oxygen depending mostly on temperature and partial pressure of oxygen in air.

Have you read somewhere that surface tension alters gas exchange? The effect in the lungs is not from surface tension directly, but that high surface tension decreases the surface area of the lungs exposed to air.

I don't think the term "surface tension" is applied correctly there, as agitating water doesn't appreciably alter the surface tension and I am not sure it is correct that surface tension alters gas exchange anyway. It would be a very hard thing to show since anything that alters the surface tension of water will be altering other properties as well.

That said, organic coatings on the surface of water (including aquarium water) will greatly limit gas exchange, and agitation breaks up those layers and does greatly increase gas exchange, and not just for the obvious reason of moving the O2 saturated surface layer of water deeper into the tank, replacing it with unsaturated water that takes up O2 faster.

 

[Mortie31]

You are correct about surface agitation increasing gas exchange. Surface tension impedes gas exchange and surface agitation decreases surface tension thereby increasing gas exchange. Gas exchange is a two way street. This includes oxygen as well. Water will only saturate a certain amount of oxygen depending mostly on temperature and partial pressure of oxygen in air. During photosynthesis, excess oxygen produced in system water leaves the water and goes to the air at the same time that carbon dioxide gas is entering the water to feed bicarbonate alkalinity to produce glucose during photosynthesis.

What I’ve found is that there seems to be a direct link with the amount of agitation and dissolved O2 levels, I’m not sure by what mechanism this happens, but furious agitation really drives the levels up far more than a gentle agitation, so much so that I’m considering whether the battery backups on my 2 vortech MPs could be better used elsewhere as they make hardly any surface disturbance due to the depth I run them at, but saying that they may circulate less dissolved O2 water towards the surface, so maybe run one and a back up on my gyres which really still the surface up..

 

[Mortie31]

You are correct about surface agitation increasing gas exchange. Surface tension impedes gas exchange and surface agitation decreases surface tension thereby increasing gas exchange. Gas exchange is a two way street. This includes oxygen as well. Water will only saturate a certain amount of oxygen depending mostly on temperature and partial pressure of oxygen in air. During photosynthesis, excess oxygen produced in system water leaves the water and goes to the air at the same time that carbon dioxide gas is entering the water to feed bicarbonate alkalinity to produce glucose during photosynthesis.

Aren’t partial pressure and saturation of O2 different from the amount of dissolved oxygen in the water? My meter reads the dissolved oxygen not sure why GHL display it as saturation really.. it’s a figure of mg/l... but I don’t pretend to fully understand this it’s mainly snippets I’ve picked up from various posts on forums.

 

[Randy Holmes-Farley]

Aren’t partial pressure and saturation of O2 different from the amount of dissolved oxygen in the water? My meter reads the dissolved oxygen not sure why GHL display it as saturation really.. it’s a figure of mg/l... but I don’t pretend to fully understand this it’s mainly snippets I’ve picked up from various posts on forums.

If you are new to O2 measurement, I'd suggest these articles:

The Need to Breathe in Reef Tanks, Part 1: Is it a Given Right? by Eric Borneman
http://www.reefkeeping.com/issues/2005-06/eb/index.php

The Need to Breathe, Part 2: Experimental Tanks by Eric Borneman
http://reefkeeping.com/issues/2005-07/eb/index.php

The Need to Breathe, Part 3: Real Tanks and Real Importance
http://reefkeeping.com/issues/2005-08/eb/index.php

 

[MInh Nguyen]

Hi Mortie31,
I just received my oxygen sensor and the card. I have both installed since last night but I couldn't get the reading. Do I need anything else beside the sensor and the card? Thank you in advance for your help.

 

[Mortie31]

Hi Mortie31,
I just received my oxygen sensor and the card. I have both installed since last night but I couldn't get the reading. Do I need anything else beside the sensor and the card? Thank you in advance for your help.

No Minh, I had to reassign my expansion box to get it to recognise it, maybe ask the question in the GHL section

 

[Subsea]

Aren’t partial pressure and saturation of O2 different from the amount of dissolved oxygen in the water? My meter reads the dissolved oxygen not sure why GHL display it as saturation really.. it’s a figure of mg/l... but I don’t pretend to fully understand this it’s mainly snippets I’ve picked up from various posts on forums.

Yes, read the articles that Randy suggested.

As I understand it, dissolved oxygen in water will reach the saturation limit as determined mostly by water temperature but if the oxygen percentage in air increases to a higher concentration, than the oxygen in the water will seek equilibrium with oxygen in the air thereby raising the saturation limit in the water. In thermodynamics, the partial pressure of gases will seek equilibrium through the molecules of the membrane that separates them. This explains why helium gas balloons always deflate in time.

 

[rock_lobster]

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.

 

[Mortie31]

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.

It may well be irrelevant, and just another thing to measure, but without measuring it how would you ever know? Maybe we’re having all sorts of issues caused by it and just don’t know...(I don’t think that’s the case having tracked it for a few months now though) but I do know I can manipulate levels easily, but do these have any benefits/ issues? I haven’t seen any yet but with everything else going on in my tank it’s hard to isolate results..

 

[Subsea]

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.

Lost all fish because of short power outage. Corals were not injured as dead fish were removed from system. Bacteria consume large quantities of oxygen 24/7. When lights go out, photosynthetic organisms consume oxygen and give of carbon dioxide which drops pH.

 

[Mortie31]

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.

If you read my post above on battery back ups and power head placement, it may sound obvious but I see so many tanks with the vortech powerheads at mid tank depth and from what I’ve experimented with they add very little dissolved oxygen.. the best way I’ve found so far of increasing O2 levels is water free falling several inches in my weir chamber... so In a power cut I would power a return pump first to keep O2 levels up and will be rethinking how I use my battery backups.. all found out by measuring O2 levels, but only by my very adhoc experiments and need to be repeated by others, but I’m changing my power outage plans based on it.

 

[Subsea]

Have you read somewhere that surface tension alters gas exchange? The effect in the lungs is not from surface tension directly, but that high surface tension decreases the surface area of the lungs exposed to air.

I don't think the term "surface tension" is applied correctly there, as agitating water doesn't appreciably alter the surface tension and I am not sure it is correct that surface tension alters gas exchange anyway. It would be a very hard thing to show since anything that alters the surface tension of water will be altering other properties as well.

That said, organic coatings on the surface of water (including aquarium water) will greatly limit gas exchange, and agitation breaks up those layers and does greatly increase gas exchange, and not just for the obvious reason of moving the O2 saturated surface layer of water deeper into the tank, replacing it with unsaturated water that takes up O2 faster.

Yes, I confused the two. Does surface tension contribute to surface film?

https://hemantmore.org.in/foundation/science/physics/surface-tension-everyday-life/2490/

 

[Randy Holmes-Farley]

Yes, I confused the two. Does surface tension contribute to surface film?

https://hemantmore.org.in/foundation/science/physics/surface-tension-everyday-life/2490/

High surface tension/surface free energy of water is what attracts organics to the surface, lowering the surface tension/surface free energy.

 

[Subsea]

@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.

 

[Subsea]

If you read my post above on battery back ups and power head placement, it may sound obvious but I see so many tanks with the vortech powerheads at mid tank depth and from what I’ve experimented with they add very little dissolved oxygen.. the best way I’ve found so far of increasing O2 levels is water free falling several inches in my weir chamber... so In a power cut I would power a return pump first to keep O2 levels up and will be rethinking how I use my battery backups.. all found out by measuring O2 levels, but only by my very adhoc experiments and need to be repeated by others, but I’m changing my power outage plans based on it.

I agree with your shift of ups priorities. Thank you for contributing to this thread.

On my 120G new build using Reverse Flow Undergravel Filter with 40G sump, I consider surface skimmer and water cascading into sump critical for gas exchange. Of equal consideration in my system is maintaining aerobic conditions in 2” of aroggonite substrate over 8 square feet.


https://www.reef2reef.com/threads/wet-salty-for-christmas-2017.428100/

 

[norfolkgarden]

If you are new to O2 measurement, I'd suggest these articles:

The Need to Breathe in Reef Tanks, Part 1: Is it a Given Right? by Eric Borneman
http://www.reefkeeping.com/issues/2005-06/eb/index.php

The Need to Breathe, Part 2: Experimental Tanks by Eric Borneman
http://reefkeeping.com/issues/2005-07/eb/index.php

The Need to Breathe, Part 3: Real Tanks and Real Importance
http://reefkeeping.com/issues/2005-08/eb/index.php

Thank you! Awesome reading!

 

[Forsaken77]

I agree with your shift of ups priorities. Thank you for contributing to this thread.

On my 120G new build using Reverse Flow Undergravel Filter with 40G sump, I consider surface skimmer and water cascading into sump critical for gas exchange. Of equal consideration in my system is maintaining aerobic conditions in 2” of aroggonite substrate over 8 square feet.


https://www.reef2reef.com/threads/wet-salty-for-christmas-2017.428100/

Aerobic bacteria will always thrive. A reverse flow UG, huh? I always thought that to be a good idea in theory, keeping particulates suspended. In practice you can end up with detritus, leftover food, stuck under the sand and channelling issues where most water exits certain locations instead of an even dispersal. Do you have pre-filters on the powerheads by any chance? I wish you luck with it.

I watched a YouTube video where the hobbyist had a nitrate problem out of control. He had something like a 150 gallon DT. First he plumbed in a 125 gallon fuge through the wall to the room next to the tank. Still had a problem. Then he plumbed in a huge tub remote deep sand bed feeding the fuge. Still, the problems persisted. What he found to finally solve the problem was using a very fine sand, Oolite, so no detritus could penetrate into the sand and was easily removed. You could see detritus swirling on the surface, but not disturbing the sand. Figured I'd try something similar.

I have roughly 190 pounds of fine sand ready to go into my new 180 build at a roughly 3" depth for anaerobic bacteria. Because there's never an issue with aerobic bacteria, anaerobic became my concern. I didn't want a DSB over 4 inches, but very fine sand 3 inches deep will hopefully be enough for an anaerobic population . I didn't go Oolite, but Fiji Pink, which is a #90 grade sand.

I used to have a 72 bow tank 20 )years ago where I never touched the sand. No vacuuming, nothing. That tank ran itself for years. I think I'm going to let my sand bed be