Questions about airstone's placement on dissolved oxygen

[James Croney]

8 hours ago, Coronal Mass Ejection Carl said:

 

Oh dear, this is the opposite of what I was hoping was the case. From what I can read on that graph though, it seems at the three-hour mark or so the oxygen levels out, to about 8mg/l in the third hour, more or less stopping the accelerated oxygenation at an hour or so in. This tells me that our tank measurements should be taken about 3to4 hours after we start the airstone.

I'm hoping that the smaller volume of water in my 3ish gallon tank will let the numbers line up for the surface bubbling to be ok. So far, all the fish seem to be happy and breathing easy. The other two fish that died before I had an airstone showed signs of being unhappy within a day and a half. So feeling like the current setup with the airstone near the top is at least sufficient for them.

 

@Daniel Given the data above, how do you feel about testing across two known times in a day? Say start the airstone at 9am, and by 12noon read the data. The next day, change the depth and re-read under the same timings. This will also baseline any noise from the amp3 as I assume the light cycle is the same over the daycycle. It may be easier than leveling out the light production.

@KBOzzie59 I did watch that video. Lots of insights there! But I didn't catch anything to do with vertical placement of the airstone. I did get a look at a young old sassy. That was funny.

[Streetwise]

I've been trying to refresh my knowledge from the biology classes I took years ago, and I was reminded that photosynthesis is an endothermic reaction, while plant respiration is exothermic. I haven't been able to find information about how much temperature would change based on these reactions.

[Daniel]

24 minutes ago, Streetwise said:

I've been trying to refresh my knowledge from the biology classes I took years ago, and I was reminded that photosynthesis is an endothermic reaction, while plant respiration is exothermic. I haven't been able to find information about how much temperature would change based on these reactions.

Honestly I don't know either. But what I do know is water has one of highest specific heat capacities of anything I have got around the house at about 4000 Joules per kilogram °C or 1 Calorie. What this means is you can pump a boatload of heat into water before you raise its temperature even 1 °F. If our aquarium plants are capable of that, to heck with firewood! I will just add more planted aquariums this winter and be happy and warm at the same time. 🙂

[James Croney]

5 minutes ago, Streetwise said:

photosynthesis is an endothermic reaction, while plant respiration is exothermic.

Ahh, I didn't know this. That would make sense in the case of the plants using available heat which would increase oxygen when the lights came on. Well, from the position of "things react when they want to" and being endothermic is 'wants' heat to be happy. Photosynthesis apparently wants heat and light to be happy. This is also interesting that the respiration is exothermic. That would lead me to think that it would release some heat and co2 all the time, even at night. I have noticed planted tanks tend to 'stay warmer' at night but always attributed it to the insulating properties of plant matter more than "plants being warm". As with everything... probably a little of both. LOL Stretching my plant brains here.

[Daniel]

Still mulling over how to take meaningful measurements for the experiment. I might just setup 2 identical aquariums side by side and move the probe back and forth between the two.

In the meaning time I am draining the aquarium the probe had been in.

[James Croney]

@DanielGiven the data above, how do you feel about testing across two known times in a day? Say start the airstone at 9am, and by 12noon read the data. The next day, change the depth and re-read under the same timings. This will also baseline any noise from the amp3 as I assume the light cycle is the same over the daycycle. It may be easier than leveling out the light production.

It may be easier than using two tanks, unless that is what you would like. Ultimately, I'm just adding data to the pile here. No hard demands. 😄

Nice python. 😉

[Daniel]

Just now, James Croney said:

This will also baseline any noise from the amp3 as I assume the light cycle is the same over the daycycle.

😉

Yes, the lights just come on in the morning and go off in the evening, pretty straight forward. And this shouldn't affect our data, but the lights do follow the rising and setting of the sun, so right now everyday the the light cycle is about 1 minute shorter than the previous day (at least for the next month, at which time the process will reverse).

[Cory]

My testing was, use the same aquariums and change the airation method. Wait several days to 1 week between tests. I started with things that wouldn't go backwards. Like having a tank top full of duck weed, then removing the duck weed. Then different airstone/powerhead/canister/hang on backs. This is why my testing took a couple of months.

[Cory]

Also make sure to test the same time every day. As with a planted tank, right when lights come on will have much lower oxygen then at the end of the day when the plants produced oxygen all day.

[Maggie]

3 hours ago, Daniel said:

Still mulling over how to take meaningful measurements for the experiment. I might just setup 2 identical aquariums side by side and move the probe back and forth between the two.

In the meaning time I am draining the aquarium the probe had been in.

You know you're a NERM when you have several spare tanks sitting around for experiments on the fly. 🙂

[Ken Burke]

Just to add to the geeky Nerm thing and adding a Fermi Problem:

The surface area of the water in an aquarium is easily calculated.  The surface area of an air bubble a little more more more complicated, but do-able.  I suspect the water touching the surface of an air bubble tuns over faster then the surface as well, limiting the saturation and improving gas exchange.  And I would guess the sum of the surface area of all those tiny bubbles in the plume is larger that the surface of the water at the top of the tank.  
 

I’m not up to estimating the size of a bubble (1mm), then the number of bubbles in the tank (50 - 100 per linear inch of the plume) But it could be done...  

[James Croney]

1 hour ago, Ken Burke said:

And I would guess the sum of the surface area of all those tiny bubbles in the plume is larger that the surface of the water at the top of the tank. 

I’m not up to estimating the size of a bubble (1mm), then the number of bubbles in the tank (50 - 100 per linear inch of the plume) But it could be done...  

It certainly seems that the smaller the bubbles the easier the oxygen absorbs. Smaller bubbles having a larger surface area makes sense. I feel like something on the bubbles 'popping' on the surface has an unexpectedly high addition to oxygen as well. Nature has usually come to a very efficient path for energy, Not sure if its for popping bubbles on the surface, just a thought.

[Daniel]

I may not be able to get to this today, but when I do this is what I am setting up for the airstone experiment. Three similar tanks without heaters or lights. Only the airstone placement will be different.

• airstone at the top
• airstone at the bottom
• no airstone at all

[Daniel]

Slowly but surely. Haven't recalibrated yet. I need to check out the Apex information that @Streetwise sent first.

[Daniel]

I haven't started the experiment proper yet. But here is what some of data looks like already.

On the left is the deep airstone. In the middle is no airstone. On the right is the airstone 1" from the surface.

So far what we can see:

• an airstone puts a least 25% more oxygen than would normally occur without an airstone.
• There is only a slight difference between airstone at the bottom and airstone near the surface.
• The airstone near the surface provides slightly better oxygenation.

[Coronal Mass Ejection Carl]

12.6 mg/L dissolved oxygen? What's the water temperature?

[TheDukeAnumber1]

37 minutes ago, Daniel said:

• The airstone near the surface provides slightly better oxygenation.

Interesting... can't wait to see what the "proper" data looks like.

[Daniel]

10 minutes ago, Coronal Mass Ejection Carl said:

12.6 mg/L dissolved oxygen? What's the water temperature?

I wondered who would catch that. I am not surprised it was @Coronal Mass Ejection Carl. Yes I have not re-calibrated the dissolved oxygen sensor so those numbers are just relative to each other.

The current temperature is about 72°F and the current DO is likely in the neighborhood of ~8.7.

That is why I indicated I didn't have proper data yet.

[Daniel]

Here is part of the friction on moving faster on this project. I want to calibrate all the probes includings the pH probes at the same time. My pH calibration solutions should have been here yesterday. But this is what I am currently seeing:

At one point yesterday, it was "Out for Delivery". I always wonder what the true story is on this. Damaged? Lost? Who knows?

[Streetwise]

Thanks for the product info! It looks like I have to recalibrate for the temperature-compensated pH option.

[Coronal Mass Ejection Carl]

44 minutes ago, Daniel said:

At one point yesterday, it was "Out for Delivery". I always wonder what the true story is on this. Damaged? Lost? Who knows?

One of my UPS packages was out for delivery and then went dark for a week before being rescheduled for delivery and actually being delivered.

Two of my Amazon orders also got lost at the same time.

There are dry format pH calibration buffers. I believe they have longer shelf lives. They certainly take up less space. You mix them up with 50-100 mL of distilled water when you need them.

pH 10 solution has the shortest shelf life so if a 2-point calibration is all you need that's the one to skip.

[Daniel]

Thank you @Coronal Mass Ejection Carl, I may try the dry next time.

[James Croney]

2 hours ago, Daniel said:

The airstone near the surface provides slightly better oxygenation.

Wow! My assumptions were backwards, if these loose-results are pointed towards the truth. I wonder if we will get onto any real secrets here. O.o Let me not get over excited. I'm already excited to see your idea of commitment to proper data. 😄

[Coronal Mass Ejection Carl]

I might be able to get some data during my next water change. I usually drain the water down until the backs of the biggest fish are exposed.

I thought about just raising the air stone during normal operations but it would probably involve kinking the air tubing and add uncertainty to the experiment.

My fish do panic when the water level is too low so some data points might to be disregarded.

It's not a lot of extra work though as all I have to do is calibrate the probe before the water change.

[Ken Burke]

6 hours ago, Daniel said:

I wondered who would catch that. I am not surprised it was @Coronal Mass Ejection Carl. Yes I have not re-calibrated the dissolved oxygen sensor so those numbers are just relative to each other.

The current temperature is about 72°F and the current DO is likely in the neighborhood of ~8.7.

That is why I indicated I didn't have proper data yet.

While not not the proper data, and insufficient to draw any conclusions, the early data is relevant as long as the temperature remained consistent.  
 

when you are taking your measurements, how do you control for stratification in the tank.  In case I’m saying it wrong - are you measuring in a “hot spot” where the dissolved O2 is higher?  (I’m guessing you have already accounted for this, but worth asking)