Dissolved Oxygen data - The Planted Tank Forum
 23Likes
Reply
 
LinkBack Thread Tools Display Modes
post #1 of 20 (permalink) Old 09-12-2020, 11:43 PM Thread Starter
Planted Tank Enthusiast
 
Capsaicin_MFK's Avatar
 
PTrader: (20/100%)
Join Date: Nov 2009
Location: MN native in Kansas
Posts: 903
Dissolved Oxygen data

I've been working a lot this summer on deploying DO, temperature, light, Chlorophyll-a, and Phycocyanin sensors in various reservoirs around the state for different projects. I had the opportunity to setup and complete an experiment looking at phosphorus release rates from sediment cores while under varying Dissolved Oxygen conditions. One of the tools I used was a DO/temperature sensor that gives real-time data through an LCD screen at 1 minute increments. Our typical sensor has a solid white housing and to retrieve data you have to plug it into a computer. I was curious to see how DO changed in a 24hr period of time in my aquarium so I placed this sensor in my 10g at 1:30pm today. I'll post the data tomorrow! I'll try to incorporate photoperiod and CO2 injection into the graph.

DO is measured in mg/L which equals ppm.
Temperature is measured in degrees Celcius.



deeda, Hendy8888, Greggz and 6 others like this.
Capsaicin_MFK is offline  
Sponsored Links
Advertisement
 
post #2 of 20 (permalink) Old 09-13-2020, 12:48 AM
Planted Tanker
 
burr740's Avatar
 
PTrader: (132/100%)
Join Date: Feb 2014
Location: Bama
Posts: 5,919
Very interesting! Thanks for sharing the results.

I would also be curious to see how an airstone affects O2 levels...if you have one of those laying around


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.




burr740 is offline  
post #3 of 20 (permalink) Old 09-13-2020, 01:37 AM Thread Starter
Planted Tank Enthusiast
 
Capsaicin_MFK's Avatar
 
PTrader: (20/100%)
Join Date: Nov 2009
Location: MN native in Kansas
Posts: 903
Quote:
Originally Posted by burr740 View Post
Very interesting! Thanks for sharing the results.

I would also be curious to see how an airstone affects O2 levels...if you have one of those laying around
Results tomorrow! This was just a snapshot of one reading about 2 hours into my photoperiod. I just walked over now and checked DO reading. It says 10.58 mg/L at 26.16 C.

I don't currently have an airpump to try that out, but I'm guessing the surface agitation would degas much of the trapped O2 from plant photosynthesis and bring it closer to 100% saturation levels for the given temperature. On a side note, I'm using an Aquaclear 20 HOB filter.
Greggz, burr740 and Immortal1 like this.
Capsaicin_MFK is offline  
 
post #4 of 20 (permalink) Old 09-13-2020, 09:26 PM Thread Starter
Planted Tank Enthusiast
 
Capsaicin_MFK's Avatar
 
PTrader: (20/100%)
Join Date: Nov 2009
Location: MN native in Kansas
Posts: 903
First picture is the raw data plotted on a graph. The second picture, I added sections to show CO2 injection(aqua) and photoperiod(yellow). CO2 goes from 5:00am - 11:00am, and again from 2:00pm - 8:00pm. Lights go from 7:00am - 12:00pm, and again from 4:00pm - 9:00pm.




Capsaicin_MFK is offline  
post #5 of 20 (permalink) Old 09-13-2020, 10:13 PM
Planted Tank Guru
 
PTrader: (0/0%)
Join Date: Feb 2017
Location: PA
Posts: 2,120
Very interesting possibilities here, but I’m having difficulty understanding what is going on in the graph.

Just focusing on actual ppm and temperature, I’m seeing a range of roughly 7-11ppm in DO and a temperature range of roughly 23-26 oC, correct?

We are also seeing a dramatic increase in DO when CO2 is on. Is the implication that this is because plants are now photosynthesizing and not respiring? How heavy would you characterize your plant mass to be and is it a high-light setup? It would also be interesting to see what the pattern is if there is no surface agitation which, I assume, would give us a clearer picture of actual plant impact upon O2.

I’m also curious about the ppm readings, e.g.; at 26 oC, the maximum ppm (100% solubility) should be about 8.2ppm at sea level pressures, but you are recording 11ppm? Further, DO ppm should rise and fall inversely to temperature, but you are recording the opposite.

All of this, if true, leads me to believe that you may be experiencing super-saturation during photosynthesis (which can harm livestock) which is briefly possible with very rapid O2 infusion or am I just not reading this graph correctly?

Lot of questions, but since you have access to this instrument, it offers the potential for a great deal of insight. Not least of the possibilities would be to use your instrument to calibrate some of the O2 test kits, such as the Salifert kit.

As a side note: does your temp vary by that >5 oF every day?
Greggz likes this.
Deanna is offline  
post #6 of 20 (permalink) Old 09-14-2020, 01:07 AM Thread Starter
Planted Tank Enthusiast
 
Capsaicin_MFK's Avatar
 
PTrader: (20/100%)
Join Date: Nov 2009
Location: MN native in Kansas
Posts: 903
Quote:
Originally Posted by Deanna View Post
Very interesting possibilities here, but I’m having difficulty understanding what is going on in the graph.

Just focusing on actual ppm and temperature, I’m seeing a range of roughly 7-11ppm in DO and a temperature range of roughly 23-26 oC, correct?

We are also seeing a dramatic increase in DO when CO2 is on. Is the implication that this is because plants are now photosynthesizing and not respiring? How heavy would you characterize your plant mass to be and is it a high-light setup? It would also be interesting to see what the pattern is if there is no surface agitation which, I assume, would give us a clearer picture of actual plant impact upon O2.

I’m also curious about the ppm readings, e.g.; at 26 oC, the maximum ppm (100% solubility) should be about 8.2ppm at sea level pressures, but you are recording 11ppm? Further, DO ppm should rise and fall inversely to temperature, but you are recording the opposite.

All of this, if true, leads me to believe that you may be experiencing super-saturation during photosynthesis (which can harm livestock) which is briefly possible with very rapid O2 infusion or am I just not reading this graph correctly?

Lot of questions, but since you have access to this instrument, it offers the potential for a great deal of insight. Not least of the possibilities would be to use your instrument to calibrate some of the O2 test kits, such as the Salifert kit.

As a side note: does your temp vary by that >5 oF every day?
Yes, the DO and Temp had the ranges you mentioned. We had the windows open all day so the temperature fluctuated just from that. It is possible to get DO above 100% saturation. This is pretty common in fast moving streams with a lot of aeration, but it is also possible in our aquariums due to the high oxygen production by plants. I don't plan on using this sensor for calibrating other test kits. It is actually getting deployed into a reservoir soon if we are unable to retrieve our sensors from the bottom of a research lake.

Plant mass is pretty heavy, and yes you see a drastic increase in DO because photosynthesis is producing oxygen. I'd say this 10g is Medium-High light. Compared to the people who have sumps/overflows, this HOB doesn't produce much surface agitation. I'm willing to bet my aquarium has lower overall DO at night than those with more agitation. I might get airstone to reduce the downward swing at night.

Here's a couple critical points recorded during the 24 hour period:

Highest Temp: 2020-09-12 @21:05:00, Temp:26.20, DO:10.73, DO Sat%:132.67
Lowest Temp: 2020-09-13 @07:25:00, Temp:22.81, DO:7.35, DO Sat%:85.35
Highest DO: 2020-09-13 @12:02:00, Temp:23.92, DO:11.06, DO Sat%:131.14
Lowest DO: 2020-09-13 @02:38:00, Temp:24.68, DO:5.97, DO Sat%:71.78

For clarity on the 2nd graph with the aqua and yellow portions, the aqua indicates the time blocks that CO2 is on, and the yellow indicates when the lights are on. You can see clear points in the DO where photosynthesis starts and stops.
Greggz and Deanna like this.

Last edited by Capsaicin_MFK; 09-14-2020 at 01:16 AM. Reason: Added info
Capsaicin_MFK is offline  
post #7 of 20 (permalink) Old 09-14-2020, 01:54 AM
Planted Tank Guru
 
PTrader: (0/0%)
Join Date: Feb 2017
Location: PA
Posts: 2,120
Thanks. I'm going to have to think about it. That's a rather dramatic saturation excess just based upon plants. Then there is the inverse relationship of DO to temp, where they seem to track each other nearly perfectly, but should be moving inversely, at least to some degree. How would you describe your fish load - light, medium, heavy? That should be countering the effects of photosynthesis at least as much as it contributes to a drop during respiration.

I can see heavy saturation in a fast moving stream that is riddled with rocks, etc., but a box of water with moderate gas exchange is troubling to me.
Deanna is offline  
post #8 of 20 (permalink) Old 09-14-2020, 02:48 AM Thread Starter
Planted Tank Enthusiast
 
Capsaicin_MFK's Avatar
 
PTrader: (20/100%)
Join Date: Nov 2009
Location: MN native in Kansas
Posts: 903
Quote:
Originally Posted by Deanna View Post
Thanks. I'm going to have to think about it. That's a rather dramatic saturation excess just based upon plants. Then there is the inverse relationship of DO to temp, where they seem to track each other nearly perfectly, but should be moving inversely, at least to some degree. How would you describe your fish load - light, medium, heavy? That should be countering the effects of photosynthesis at least as much as it contributes to a drop during respiration.

I can see heavy saturation in a fast moving stream that is riddled with rocks, etc., but a box of water with moderate gas exchange is troubling to me.
Yes, when you only look at DO vs Temp, it has an inverse relationship with saturation points (i.e. cold water has higher DO saturation, and hot water has lower DO saturation). I think the change in temperature might affect the DO curve slightly if I could keep it consistent for the 24 hours. I can test again and bug my wife not to open the windows for a day to keep the house temp the same. I have the heater in the aquarium set to 72F/22C, so the house getting up to 78F/26C was inevitably going to raise the water temp. You can see at 7:30am when my wife closed the windows and turned on the furnace, as there is almost a V shape to the temp graph.

The graph correlations you are seeing between DO and Temp are totally coincidental because the house got hot during the day and colder at night. This does mimic the real world though as lakes and reservoirs do the same thing in the Littoral Zones where aquatic plants grow. Warmer temps during the day with higher DO because of photosynthesis, and colder temps at night with lower DO due to respiration.

In this 10g I have 2 cherry barbs, 6 pygmy cories, 2 dwarf gourami.
Capsaicin_MFK is offline  
post #9 of 20 (permalink) Old 09-14-2020, 03:12 AM
Planted Tank Guru
 
PTrader: (0/0%)
Join Date: Feb 2017
Location: PA
Posts: 2,120
By any chance, can you take accurate pH measurements at the points before and after lights on and off? It would be interesting to see if CO2 is moving by such significant rates. Maybe it has a sensitivity to tank size.

I use a Salifert O2 kit to gauge relative levels and have been able to calibrate it ... crudely. My setup is quite a bit different and my tank is 3x yours. I run CO2 24/7 and a surface skimmer 24/7 with steady temps 24/7. I can move that kit O2 reading down by about 30% by turning off the skimmer, but I can't move the O2 by comparing lights on to lights off (remains stable). I have a heavy plant mass with high light. I estimate that the skimmer maintains O2 at about 100% saturation given my temps.
Greggz likes this.

Last edited by Deanna; 09-14-2020 at 03:23 AM. Reason: add
Deanna is offline  
post #10 of 20 (permalink) Old 09-14-2020, 03:34 AM Thread Starter
Planted Tank Enthusiast
 
Capsaicin_MFK's Avatar
 
PTrader: (20/100%)
Join Date: Nov 2009
Location: MN native in Kansas
Posts: 903
Quote:
Originally Posted by Deanna View Post
By any chance, can you take accurate pH measurements at the points before and after lights on and off? It would be interesting to see if CO2 is moving by such significant rates. Maybe it has a sensitivity to tank size.
I don't have a pH sensor available to use. The one we use looks like this...



Bump:
Quote:
Originally Posted by Deanna View Post
I estimate that the skimmer maintains O2 at about 100% saturation given my temps.
If you give water more surface agitation, it will try to meet an equilibrium point with O2 in the air, which is that 100% saturation point you are looking at.

For example, I just completed a sediment core incubation study where 3 of my core samples were being aerated by an aquarium airpump 24/7, but since there were no plants in the core tubes and they were in the dark, there was no photosynthetic activity to add in more oxygen. The cores were in a constant 20C environment, so 100% DO Saturation would be 9.1 ppm (mg/L). My cores sat at about 8.3 ppm DO for 10 days straight. My other cores got N2 gas injected into the water and they had DO levels around 0.10 ppm.
Capsaicin_MFK is offline  
post #11 of 20 (permalink) Old 09-14-2020, 12:59 PM
Planted Tank Guru
 
PTrader: (0/0%)
Join Date: Feb 2017
Location: PA
Posts: 2,120
The swings you are seeing are much greater than I would have expected, particularly as temps are dropping. As we’ve been discussing, it must be primarily related to a significant reduction in agitation as compared to what I have.

I would be concerned with the extreme points that you reach at max photosynthesis and max respiration. My understanding of stress issues with fish is that below ~8ppm O2 and many tropical fish begin to struggle. Then, above ~130% O2 saturation, gas bubble disease may creep in causing it’s own share of damage, but may not show up directly at lower supersaturation levels, instead resulting in secondary problems such as susceptibility to other vectors.

I think that the best take-away from your interesting study, albeit obviously limited, is that ensuring good gas exchange is very important from both the CO2 standpoint and the O2 standpoint, which we don’t often consider in view of O2 contribution from photosynthesis.

As I mentioned, given your tanks’ ability to show such wide swings, it would be very interesting to add an estimate of the CO2 swings that might be occurring vis--vis these O2 recordings.

Thanks for sharing all of this.
Deanna is offline  
post #12 of 20 (permalink) Old 09-14-2020, 03:07 PM
Planted Tank Obsessed
 
Mark Fisher's Avatar
 
PTrader: (0/0%)
Join Date: Dec 2011
Location: Rockport, Texas
Posts: 472
Quote:
Originally Posted by Deanna View Post
I would be concerned with the extreme points that you reach at max photosynthesis and max respiration. My understanding of stress issues with fish is that below ~8ppm O2 and many tropical fish begin to struggle.
O2 saturation at 79F is 8.1 ppm, and at 83F it is 7.8 ppm. Stress from hypoxia occurs at lower levels, ~3 ppm, not at saturation.
Mark Fisher is offline  
post #13 of 20 (permalink) Old 09-14-2020, 04:49 PM Thread Starter
Planted Tank Enthusiast
 
Capsaicin_MFK's Avatar
 
PTrader: (20/100%)
Join Date: Nov 2009
Location: MN native in Kansas
Posts: 903
Quote:
Originally Posted by Mark Fisher View Post
O2 saturation at 79F is 8.1 ppm, and at 83F it is 7.8 ppm. Stress from hypoxia occurs at lower levels, ~3 ppm, not at saturation.
Correct.

0 - 0.50 ppm DO = anoxic
0.50 - 2.00 ppm DO = hypoxic
>2.00 ppm DO = oxic
Econde likes this.
Capsaicin_MFK is offline  
post #14 of 20 (permalink) Old 09-14-2020, 10:34 PM
Algae Grower
 
Ordinary Joe's Avatar
 
PTrader: (0/0%)
Join Date: Feb 2020
Posts: 31
Really interesting results! The tendencies in the saturation curve seems somewhat expected to me, but I didn't expect the O2 to reach these levels of supersaturation. I think if the temperature was constant and at the upper range (26oC), you would get even higher O2 saturation, due to increased plant photosynthesis, although it would also increase respiration and this may compensate the increase in O2 production.

Anyways, it would be nice if we had the same kind of data from different aquariums to compare, but I know these oxygen meters are not cheap.


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
Ordinary Joe is offline  
post #15 of 20 (permalink) Old 09-15-2020, 12:44 AM Thread Starter
Planted Tank Enthusiast
 
Capsaicin_MFK's Avatar
 
PTrader: (20/100%)
Join Date: Nov 2009
Location: MN native in Kansas
Posts: 903
Quote:
Originally Posted by Ordinary Joe View Post
Really interesting results! The tendencies in the saturation curve seems somewhat expected to me, but I didn't expect the O2 to reach these levels of supersaturation. I think if the temperature was constant and at the upper range (26oC), you would get even higher O2 saturation, due to increased plant photosynthesis, although it would also increase respiration and this may compensate the increase in O2 production.

Anyways, it would be nice if we had the same kind of data from different aquariums to compare, but I know these oxygen meters are not cheap.
Oh yeah, I would love to test a similarly stocked aquarium that uses and overflow/sump to compare. I'm willing to bet the DO Sat% stays lower during peak photosythesis and stays higher at night due to increased surface agitation. Basically, the curve gets flatter.

Increasing temperature would lower the O2 saturation level, but would increase overall biological growth. I guess there is only one way to find out if the curve changes based on a constant temp at the upper range...ANOTHER TEST!

I will set the heater to maintain a constant 78F/26C and record another 24 hours.
Ordinary Joe likes this.
Capsaicin_MFK is offline  
Reply

Tags
None

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the The Planted Tank Forum forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in










Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome