Pond Boss Forums AQUATIC VEGETATION Controlling unwanted plants Fish kill as my Reward

I just got back from netting most of the remaining dead rainbow and brown trout out of my small (about .12 acre surface area) pond here at 7800ft in Colorado. 4 days ago I sprayed about 15 oz of Reward to less than 1/10 of the area of my pond to kill off the elodea that is choking everything. There's still lots of alive looking weeds, but most all of my fish over 6" are dead. Of course, this act coinsides with the start of our hottest period yet this summer. Will check water temps tomorrow but it's got to be a DO crash. Bummer all around.
My question is this: how do I know when I can restock my pond? I plan on raking out the dead elodea over the next week or 2. I'm thinking that I could just keep using the Reward to get rid of as much of the elodea as possible. Then when things cool down tempature wise, I'll restock. And I'm thinking that I will finally have to invest in a DO meter - if so, any suggestions on what kind to get and where to get it from?
Thanks, Barbara

Sorry to hear about your fish kill Barbara. Here are some discussions regarding O2 meters..

DO Meter Advice

affordable DO meter?

Battling Elodea is no fun.

Sorry to hear about your fish kill.

If most fish died and a re-stocking will be in the works, I would go ahead and make sure the Elodia was eliminated now by whatever means first.

Larger trout are readily available and relatively inexpensive.

+1. Kill off all vegetation, drain, do whatever improvements you've always wanted to do, refill, restock.

Reward is not approved for use in the water and killed far hardier fish than trout.

What ? Reward is approved for aquatic use. Here is the label.

http://www.midwestaquacare.com/product-labels/Reward.pdf

I was under the impression Diquat was rough on birds but not that bad for fish. Maybe the dying plants plus the other factors combined for the die off. Personally if I used that little Reward and followed instructions to the letter I would contact them and complain loudly. That is not supposed to happen, but as I always say, those smaller ponds just have little room for bad conditions. Sorry to hear about your tragic die off.

Thanks for the replies. I can't drain the pond, and my water source at this time of year is whatever rainfall we get, so I can't refill it either. I will get as much elodea out of it as I can before I restock once it cools down. Barbara

Rex has got to be thinking of Roundup instead of Reward. I treated our pond with a Reward/Cutrine mix and did not have any problems of fish dying.

Roundup instead of Reward, you lost me there.

Don't feel bad PF, I almost never know what I'm talking about.

Oops....I WAS thinking of Roundup....My bad!!!

No JHAP, my brain was malfunctioning with temporary flatulence. My bad.

All,
My water temps taken yesterday about 1pm. were 70 degrees aobut 2 feet deep, and 68 at the deepest point, about 8 feet down. I have an aerator that I had been running overnight, but it's output is minimal at this time (I have a fox that likes to bite the black polypipe that carries the air from the pump to the pond, and I think he's been at it again!).
Now of course, my pond doesn't smell very good (unless you're the bear).
Barbara

Of course you know trout just are not going to survive let alone thrive in those temps. I don't think Reward has anything to do with this, a nonfactor. Trout can only last so long in water temps that high. Ideal temps for most is in the 40's. Other negatives with those water temps could include faster decomposition of decaying vegetable matter. Less dissolved O2, faster evap rates. I could be reaching here without seeing it, but I do not think your pond is meant to be a long term year round trout pond.

I wonder if wrapping the air pipe in copper wool (like steel wool) would discourage the fox. Bats and mice won't chew on it.

I respecfully disagree. 68 is not lethal for trout although it would be better if it was lower. If there was plenty of oxygen it wouldn't be an issue, but considering she's got decomposing weeds...

When to many stressors are at work the combo of them can kill at levels where any one of them would not be lethal.

I agree that 68* is not lethal, but the trout's immune system is so depressed, any slight infection or injury could easily kill it.

Like ewest said...."When to many stressors are at work the combo of them can kill at levels where any one of them would not be lethal."

I've had fish in my pond now for several years, and only once did I have to do supplemental aeration with a big trash pump to keep fish from dying at 70+ degrees. I'm pretty sure the decomposing weeds, plus turning off the photosynthesis dropped the O2 levels and killed the fish.
But how do I know when it's Ok to restock? By DO level? By water temperature? Once the weeds are done decomposing? and how do you know?

Trout just need colder water to thrive. Did the temp kill them alone? No. But it started the clock of death clicking. All you need is one little event to make it strike 12. No way those trout go belly up if you Reward it with 50 degree temps. I would make the pond better for trout before I put any more in.