Pond Boss Forums INTRO Questions & Observations Fish Kill Question........

I've sprayed Roundup around my pond for 20+ years without any adverse effect on my fish........ Have experienced a fish kill 24 hours after spraying, the last two times I've sprayed this summer. I'm careful not to spray directly into the water & there was no run off rain involved. Why suddenly is this happening?

Although strange that it has happened twice, Roundup is unlikely a contributing factor - assuming you weren't treating aquatic vegetation.
Did any unusual weather events coincide with those two treatments?
Some details about the fish-kills would be helpful. Specie(s)? Big fish? Small fish? Both? Did they seem oxygen-stressed or lethargic before dieing? Are you aerating the pond? etc

No unusual weather...... No aquatic spray... I've lost 15 CF in the 3-5 # range, lots of hybrid BG & a hoard of shiners.... All seemed oxygen deprived.... No areation being used.

Have you checked the water-temp at different depths? Actually, how deep is the pond (max and avg)?
Any significant weed or algae populations in the pond?
Is the water colored a deep/dark green - or, does it have any floating layers of bright green material?

Haven't checked the temp.....Current average depth of about 6-8'/ 10'max. No vegetation..... Water has turned a murky chocolate color. Pond surface area is about 3/4 A, 20+ ft deep when full....

Sounds like a "turn-over", resulting from thermally-statified water in the absence of adequate water-column circulation.

If this sounds confusing, it basically means that anoxic (non-oxygenated) cooler water from deeper areas of the pond rapidly mixed with warmer/oxygenated surface-water (possibly in response to a weather event, cold rain, etc) - producing a net level of dissolved-oxygen that was insufficient for fish-survival. Small/deep ponds that lack natural or artificial circulation seem notoriously susceptible to this scenario.
Lots of discussion on this subject in the "Aeration" section of the forum.

Thanks Kelly! This sheds some light on these strange turn of events.... I was kicking myself for having sprayed Roundup, but still could make no sense of it all.... Guess it was just coincidence... I'll do some homework in the aeration section.