I didn't think it was possible.

My arrogance was almost palpable as I discussed my brilliant horizontal aeration, surface agitated pond, and all of the wonderful fish that I was growing in it.

The year started out great.

I was regularly monitoring dissolved oxygen (DO), and was seeing numbers near or at saturation.

The fish were in beautiful shape and seemingly growing by the day.

The beginning of the problem apparently was in early May. A nice healthy looking bloom of submergent vegetation was taking hold. A big thick band of horned pondweed encircled the pond. About eight feet wide, it was green and vibrant and full of tens of thousands of invertebrates.

And producing oxygen by the pound I might add.

Things were going so well that I quit the hassle of taking oxygen readings in mid-June.

A little mini bloom of single celled algae followed the end of June, and Secchi readings dropped to an acceptable 24 inches and went into a holding pattern.

Water temperatures were in the upper 70's and life was good.

A few statistics for you.

1. The pond is .15 surface acre and contains about a quarter million gallons of water.

2. I'm injecting 20 gpm of well water.

3. The water is injected in with two sweeper nozzles, creating a significant circulating effect.

4. A surface agitator runs at night to give me a redundant oxygen source to protect against a well shut off, or other emergencies.

The pond has anywhere from 250 pounds to 300 pounds of fish, including bluegill, yellow perch, redears, smallies, etc.

Here's where it gets interesting.

I've found that the best way to assess the health of a pond is to fish it.

If you throw in a night crawler (sometimes I don't even use a hook), the fish should hammer it immediately, and you know all is well. It's a fool proof method. If DO levels are low, fish don't bite.

Another way of assessing the health of the pond is to observe feeding behavior. Rapid consumption of food means healthy fish.

Up until the third week in July everything was great.

Then the signs started.

Feeding levels began to drop off.

The thick band of vegetation began to regress.

The water smelled a little funny and took on a distinctive brown appearance.

The frogs started to disappear.

Then the worm was ignored.

For some reason all of this snuck up on me in a few days and it wasn't registering that I really had a problem. There's NO WAY I could be having a problems with all that circulation, aeration and fresh water.

Carbon dioxide had hit a long, fly ball straight for the warning track.

Was I going to be Willie Mays and make a beautiful over the shoulder basket catch?

Or was I going to be Jose Canseco and let the ball hit me square in the noggin and bounce into the third row for a home run?

Now I need to do two things, and in the following order.

Take appropriate action, and figure out what the heck was going on.

I took the following steps.

1. Turned the agitator on full time. This should add much needed oxygen.

2. Turn off the feeder. Dying fish don't need decaying pellets.

3. Add more fresh water. Hoping to push some of the cruddy water out the overflow.

4. Pray.

I took an oxygen reading before I took the aforementioned actions and found the following.

DO readings were 4 ppm in the top two feet of the water column, and 2 ppm at the bottom two feet.

It's obvious that the circulation and aeration were providing some oxygen, but not enough to keep up with....what?

OK, here my assessment based on observed facts.

My horned pondweed represented a "monoculture". A good 90 percent of my rooted vegetation was represented by this one species.

Some kind of environmental effect, such as increasing temperatures, or photoperiod, or some other such evil, caused the horned pond weed to die off. This occurred over a relatively short period. Seven days is my best guess.

During these seven days, the massive amount of dying submergent vegetation began to draw heavily on my oxygen reserves. The rotting veggies were subtracting oxygen more quickly than my devices could add.

My surface aerator kept the oxygen levels at sublethal values, so I didn't have an immediate fish kill.

Yellow perch found the lower, deeper oxygen levels to be intolerable, so they were forced to rise into the shallower levels, but encountered water that was too hot (pushing 90 degrees) and began to stress.

I lost 18 of my very best yellow perch over the next week, but their observed amounts of decay indicated to me that they all died around the same time, about one to two days before I realized what was going on, and they bubbled up, about three each day.

The bluegill were able to survive by milling around the agitator, which I saw them do, and I didn't kill any, although I'm sure I didn't do them any favors. I'm sure their overall health will take a while to return to pre-stress levels.

This evening I went to the pond for the first time since taking a California vacation.

The pond was looking much better.

A nice, light green new algae bloom was returning, and the fish were biting like crazy.

I'm expecting to find a few additional mortalities, but eighteen perch only represents about ten percent of the individuals present in the pond. My experience tells me that I killed at least two fish for every one that I found. Probably closer to three.

Was I Willie Mays, and make the dramatic crowd pleasing catch?

Heck no.

But was I Jose Canseco and let carbon monoxide go yard?

Not exactly.

I'm probably somewhere in between.

I'm a decent, second year outfielder who's playing in anonimity for the Royals, or Blue Jays, and the ball tipped off the edge of my glove, hit the wall and ended up being a stand-up double.

But I can live with that.

I'll do better next time.

Holding a redear sunfish is like running with scissors.