Pond Boss Forums GENERAL QUESTIONS Water chemistry Farm Pond Green Overnight Dead Fish

1/4 acre farm pond went completely light green over night. I have dead bass, catfish, and minnows all over. I see a ton of small minnows on the surface swimming around. Not sure what happened? Any ideas?

Perhaps a dissolved oxygen sag during a bloom in the pond.

Can you get any kind of aeration going? Even using a trolling motor to move water horizontally may help.

Two rules of fish kills:
1. There are more fish dead than what you can see.
2.. There are more fish left alive than you can believe.

Assess what fish are left, figure out what and how to replace those lost, and make changes to try and prevent it from happening again. I've done it 4 or 5 times now.

The bloom used up all the O2 at night because the sun wasn't out, so the fish suffocated. An aerator would have eliminated that issue.

Cody note: An aerator may not eliminate a fish kill depending on the type and size. Most all aerators will reduce the size or extent of a fish kill.

What would happen in the event of a power failure to a pond with a aeration system. Would that create a fish kill?
Thanks,
gethooked
3 Ponds : 3 acre ,1.5 acre and 3/4 acre LMB BG WC GC

gethooked, I think there's no clear answer on that as it depends on how 'good' the aeration was keeping the water. Some ponds don't really need aeration, so if their power went out, there'd be more time before a catastrophic decline in DO.

gethooked - ""the event of a power failure to a pond with a aeration system - Would that create a fish kill?"
Sunil has good advice to get this answer rolling.
Lack of aeration or shutting it off may or may not cause a fish kill. In most cases no kill would happen soon thereafter - however in some cases with pond having dense green water from lots of algae or a large amount of underwater weeds a fish kill would be more likely especially if there were several cloudy days where the plants would at night consume enough dissolved oxygen, the DO would become too low and fish would start dying, The more cloudy days the more likely a fish kill can happen especially in June July August with warmest pondwater conditions of the year. Warm water 'holds' less, thus has DO than cooler water. Those dying first usually are the largest fish because they require more oxygen compared to small fish. Bigger biomass means more oxygen is needed per individual.

Let me rephrase that. A properly sized aerator, run through the night most likely would have eliminated that issue.

Dr. Perca, how's that now? LOL


Water quality and knowing your biochemical O2 load on the pond all comes into play. For instance, take two ponds, with the same water volume and amount of fish in it. One pond has a dense algal bloom (higher biochemical O2 demand), another has 60" visibility. What one do you think would have the biggest issue in regards to low O2 levels right before sunrise?

esshup says "A properly sized aerator, run through the night most likely would have eliminated that issue."

esshup - I like the wording of "most likely"!
Better more detailed wording is always good. "eliminate a fish kill" are words that mean too definite or too absolute when dealing with nature and a wide variety of possible pond conditions.
Even with a good aeration system there can be times when DO sags can occur in remote sections of a pond with a dense algae bloom even though the aeration system was "properly sized". Some ponds that have had little sunshine during the prior day/s, a very dense algae bloom and an overloaded biomass of fish will have a huge oxygen demand at night. In those extreme situations different types of supplemental or emergency aeration such as paddle wheel or surface splashers can be necessary during the day and night to eliminate fish kills. These surface type of aerators as you know are commonly used in large commercial fish operations to eliminate or minimize fish kills. "Eliminate" is a pretty strong and incorrect word for some extreme or unique situations when dealing with nature.

Question was - " "Water quality and knowing your biochemical O2 load on the pond all comes into play. For instance, take two ponds, with the same water volume and amount of fish in it. One pond has a dense algal bloom (higher biochemical O2 demand aka BOD), another has 60" visibility. What one do you think would have the biggest issue in regards to low O2 levels right before sunrise? ""

Okay - Given the stated conditions for the two ponds - the pond with dense algae bloom and lower water visibility - by the "book" generally this pond would or should have lower DO levels right before sunrise.
However there can be numerous exceptions to this scenario due to maybe other important differences between the two ponds. There are numerous other or different important factors that can influence higher biochemical O2 demand (BOD) both day and night rather than a dense algae bloom in ponds with same volume of water and amount of fish. Different factors such as: overall organic load, wind exposure, different species or SIZES of fish with the amount or fish biomass being the same, water stain / dye differences, zooplankton community differences, submerged weed population differences, are there time of year differences, pond surface areas of the two can be significantly different due to different average depths plus some other factors while the water volumes of the two ponds were the same. Water chemistries can be different between the two ponds which is the influence of the chemical part of biochemical oxygen demand.

"May" and "Might" are two good weasel words to avoid certainty. However, they are correct words to use when giving advice as we all know "it all depends"!!!! Nothing in the pond world is certain, except uncertainty.