Pond Boss Forums INTRO Questions & Observations Fish Kill

Ok.

I did calibrate the MW600 per their instructions and I allowed the meter to stabilize before taking a reading. The meter is new to me but the calibration process seemed pretty straightforward. I'll recalibrate tonight and take another batch of readings.

I also moved the meter back and forth in the water to ensure I was getting an accurate reading.

What is the maximum DO saturation in water that is 84 degrees?

Charlie, look here for the numbers,

O2 Table from YSI


At 84f with no salt or Chlorine, about 7.69 PPM is what I read.

Here is what I see. Most folks that have a fish kill have to have something to pin it on. Of course its natural right. Just like George the other day was mad because he had a fish kill and it was with a Vertex system.... but was it really his systems fault??? Most times I think not. I think most of the time when something like this happens we myself included could 90 percent of the time look in the mirror to find the cause of our fish kill......

RC

I'm not remotely qualified to comment on aeration, but I did pick up on a couple things by watching and listening to Ted and Sue on Saturday, and I now realize more than ever that the science of proper aeration is just that...a science. Watching Ted and Highflyer checking the data, and verifying the conditions under which the testing was done, was an eye-opener for me. There's a lot that goes into making those bubbles, or at least there needs to be in order for it to be done correctly.

I was also impressed with the reasons behind the testing. At no time did I ever hear anyone say that homebuilt systems were always inadequate, or a bad idea....the concern was that one needed to source the correct components for a DIY system, including consulting with a pro for advice on the matter. It's simply not enough to make bubbles, nor is the appearance of bubbles on the surface a good indicator that all is well. My perception was that the parties involved were simply trying to ensure that PondBoss continues to provide the best information possible, from all sides, in order to help everyone make the best possible decisions.

It does appear that the folks with commercial interests at Scott’s meetng are beating up on the DIY folks, but I am sure this is not intentional.
I do know that all the science and engineering being quoted above cannot control all of the variables nature throws at a real world situation.

To correct the record, my fish kill stated above by RC51 was not the result of falure of a Vertex system, but a record drought changing a 2 acre pond into 1 acre pond with 2 acre biomass.
A bottom diffuser aeration system alone cannot prevent a fish kill under these circmstances.
George

Hey george that's what I meant it wasn't your system that failed it was a special situation that's caused your fish kill. I also believe thats what happened to Charlie. To many variables involved to just blame his air system?

Rc

Actually highflyer you can get supersaturation rates from algae blooms that exceed that. I suspect that may be what is going on here if the readings are accurate. It would also explain low oxygen readings below that due to a combination of an algae bloom blocking out sunlight, and decomposing vegetation below from too aggressive of a herbicide treatment.

Anyone else concur? And no hard feelings if you totally disagree.

See my post above.

Ok I recalibrated the meter for the 3rd time, replaced the membrane and used zero oxygen calibration solution. The meter still seemed to think it is dead on, very slight if any adjust was required. I might rent a YSI meter tonight to see if it shows anything different. Below are the readings from last night at 8:30pm and this morning at 6:30pm. My readings in the early evening are still show above the maximum saturation levels discussed above which is driving me nuts...

Updated DO reading from
8:30pm 7/23 and 6:30am 7/24

Near Surface Aerator
8:30pm 6:30AM
12" 9.2 7.0
24" 8.9 6.5
60" 8.4 6.3

Dam
8:30pm 6:30AM
12" 14.5 6.4
24" 11.0 6.3
60" 5.0 4.5

Middle
8:30pm 6:30AM
12" 13.3 6.6
24" 13.0 6.3
60" 4.0 5.7

I guess if these readings are not possible based on the maximum DO saturation maybe I have a bad meter...

If I were to invest in a 2 HP Kasco Surface aerator to hopefully eliminate the chance I deal with this situation again the future, what would the suggest run schedule be? June-August 12 hours at night? Would its rated 6 lbs of O2 per hour supply more than enough O2 running only at night?

Grabbing these DO readings all the time is a chore...

Charlie, I sent you an e-mail to the addy that's listed in your profile asking about the pond depth at certain areas that were marked on the map.

Charlie,

Forgive me if you've already posted this but when a thread gets this long I get lazy. :-)

Anyway a question:

Do you have an algae bloom (greenish or brownish water)? If so what is your water clarity? And if so, has it increased since you treated your weed problem with a herbicide?

After a macrophyte die off it's very common for the phytoplankton or filamentous algae to take over to use nutrients -- especially those nutrients that are being mixed into the water column from the decomposing vegetation via the diffusers.

Saturation rates that exceed 100 percent during the day are not unusual with an algae bloom. This is know as "supersaturation." However just a few feet below that you will see a quick drop in saturation which is what I think I've seen in your first post.

One potential problem with an algae bloom that is so intense it causes supersaturation, is it can reverse at night. Supersaturation of oxygen during that day rarely is a problem for fish though and they can go a little deeper if it's uncomfortable.

My small 1/10th acre yellow perch fry production pond is prone to an intense algae bloom. Once an algae bloom gets established it often goes extreme. No problem during the day but if I didn't run the Kasco surface aerator during the night I would have hundreds of fry piping on the surface just before daybreak.

One of the primary factors which algae blooms influence is the dissolved oxygen content of the water. During the day, the masses of algae produce so much oxygen that the water becomes supersaturated. Then, at night, the algae actually use up oxygen in the water and can cause such extremely low dissolved oxygen levels that fish kills may result.

http://water.me.vccs.edu/exam_prep/algae.htm

Cecil - The water does seem darker than normal and visibility is only about 4-6". In the past I have had visibility of around 12-16". There also seems to be a lot of suspended material, I assume dead coontail from the herbicide treatment almost a month ago.

It's good to hear that my meter is maybe not completely unreliable based on the reading it has been producing. One thing that is clear my early morning readings for the last few days are a massive improvement of where they were at as late as Monday morning.

Cecil, charlie was looking for a maximum O2 level reading for 84f. While the maximum number is probably really high, the saturation level is a good place to start and it was the only table I could find easily to help add to the learning going on. If you have a chart that shows the MAXIMUM O2 levels, I too would love to see it. I also understand supersaturation, but I thought that might be outside the scope of this thread. While 50 PPM O2 is possible, the effort would be considerable (read extreme) and definitely not worth the cost or effort, besides, your fish would be dead of O2 poisoning long before then.

Maybe I am missing the point of this thread. Isn't it to help Charlie understand normal O2 levels and how killing all of your vegetation at once is a really bad thing? That the depletion of your O2 by decomposition is inevitable when you kill off all of your vegetation and unless you have the right size surface aeration to add the needed O2, If you don't have the right sized surface aerator during one of those events, you are likely to have problems (read fish kill).

Please let me know if I am wrong.

I appreciate everyone's input. As I mentioned earlier, I am a new pond owner and obviously have a lot to learn. And learning all the aspects of pond mgmt and some of the chemical makeup is very interesting to me.

I got into this situation by going with what I thought was good advice on treating the pond with Reward from a local pond mgmt company, and a little reading here. The pond mgmt co told me they would treat the entire pond at once, but if I wanted to do it myself there was no magic to it. It was supposed to slowly kill the plant so we would not experience a DO crash... Based on reading this forum I decided to break up the treatment into 50% at the time separated by 3 weeks to lessen the likely hood of any DO issues. But apparently my plan was flawed, maybe no measurable rain for the last 3-4 weeks also contributed after a wet spring, not sure. The only thing that I am sure about is that many fish were lost. I don't have any idea of what percentage of fish may have been lost. That's another topic after the issue that got us here is resolved.

I hope to learn in this process how to prevent this from happening again, especially if I find myself in a situation to again feel the need to treat the pond with a herbicide - which will be very tough decision. The pond had a lot of coontail, to the point it really wasn't good for fishing or much of anything else during the summer months.

If a properly sized surface aerator is the only real safety net then we will probably have to go that route. And if that is the best course of action, I am curious about what type of schedule you experts would recommend, I can't imagine just keeping an eye on things and turning it on when it's likely already too late.

I appreciate everyone's input this has been a great learning experience, I obviously have a lot left to learn. And by posting this experience I hope others will be able to make better decisions when it comes to herbicide treatment in ponds with a lot of plant growth.

Thanks!

Just a quick update... DO readings from a calibrated WM600 were compared with a professional calibrated YSI556 and the MW600 reading consistently show better DO reading than the YSI. Due to the professional calibration of the YSI, and it being a professional device I think it is safe to say the MW600 is not providing the correct readings.

The YSI shows I still need help with DO readings at 6:30 am this morning from 5.45-3.72 which it also shows a saturation level of 50-45% and the MW600 at the exact same areas and depths shows DO of 7.7-7.0.

Readings the evening before at 6pm on 7/25 from the YSI were 7.99-4.6 and the MW600 12.2-6.8

Luckily I found an equipment rental shop in Olathe, KS that was very helpful. If anyone else in the KC area wants to rent a meter for testing their DO fieldenvironmental.com can help.

The YSI556 provides a slew of info, much of which I still need to research but you other that might be interested I'll post the other specs.

Water temp was consistently 23.96c, PH was steady at 7.7 and ORP was 77.6-71.5.

If I add a 2 HP Kasco Surface Aerator what would you guys recommend for the running schedule. Would 24/7 during the summer months be the best bet? Then after summer slowly phase it out?

Thanks!