Okay, so a little background... my pond is about half acre, rectangular, and I would say at least 25 years old. I am in northwest Ohio . The ground is all clay. I have a bubble aerator with a single diffuser in the middle of my pond ran by a 1/4 horse rocking piston compressor that I was running 24 hours a day after the proper startup procedure. My pond is stocked with bluegill , largemouth bass , 3 amur, and catfish (maybe only 6 cats). My ratio of bass to Bluegill is correct. In early spring I noticed a couple of my bluegill had white patches on them. I did some reading and didn't think much of it. The weekend after Memorial Day weekend, we got 5 inches of rain in one day. The pond got pretty high, reaching about two feet from the flood water from a nearby Field. I'm not sure if that had anything to do with it. About a month later, the air temperature got to the upper 90s for a few weeks. I have been feeding my fish pellet food one time a day for about a month at that point. The bluegill would instantly come to the food. About 2 to 3 weeks after the high temperatures, I went out to feed the fish. I threw a small handful of food and no fish showed up. So I looked around and I could see about 7 floating bluegill in my pond. They were bloated and their eyes were bulging, that might just be because they were dead or possibly driven by what was the cause of their death. Since then, I have had a total of maybe 24 bluegill that have died and 3 bass (at least that's what I have counted that have come to the surface) . Initially the dead bluegill were all my bigger bluegill. Maybe that's just because they were the only ones that floated to the surface and possibly didn't get eaten by catfish or bass. By this time, I pretty well forgot about the couple bluegill I saw with white patches. Over the last two weeks, I have only may be found two dead bluegill. I have started to feed again (a very small amount). When I was feeding yesterday, I saw a bluegill with white patches again and one other BG that had a small white spot by its dorsal fin. I would have thought they were scuffs from a bass or catfish trying to eat it, and maybe they are, but with the fish kill, I didn't want to take any chances. I had my water tested, and they only really tested the phosphate level. They said it was a little high, but it hasn't caused any noticeable algae bloom or weed growth. If anybody has any other ideas, I would love to hear them. Lastly, when I got my water tested they recommended I shut off my bubbler when the temperature is above 90, so I have been doing that. There are still a good amount of bluegill in the pond (I have only noticed two of them that had any white spots) I have seen at least one catfish, as well as a couple schools of minnows, not to mention a bunch of tadpoles. A curve ball is none of the dead fish have had white spots. I'm sorry this post is so long but I'm trying to cover all the information that might be needed to help me out. Thanks in advance. As soon as I figure out how to add pictures, I will.

Al,

I am sorry to hear about your lost fish. You didn't mention what type of feed you feed. For your BG it should be a feed specially formulated for predator fish.

The dead fish do look old to me and so I think it may be possible it was old age coupled with stressful environmental conditions that killed them. Because of stress, you saw them succumb in narrow band of time. There could be something else that you need to be concerned about but the fish look to me like they were already near the end of life.

Thanks for the help jpsdad. I've been feeding Purina game fish chow.

Saprolegnia…
Salt (straight stock salt) can be added to water to help with this. I wish I could give you an exact dose but I can't.
Only thing I am aware of that will clear this up but it usually starts due to stress-as jpsdad states above.

BG actually perform on grain based protein feed as do CC...I don't use grain based feed, but many choose the cheaper option to grow their BG and CC. Just wanted to clarify that point.

I doubt that the feed is the problem. Like TJ, I don't use Purina but have often used it with no problem.

The problem will almost certainly be environmental and the runoff from fields is a wild card. Fish that are feed trained that don't come to feed are unusual in a healthy pond. BTW, in a fish kill, 95% of the fish don't float.

I would have a complete water test done. Aquarium stores can probably do this.

No idea whether the mixing of water from aeration could be a problem.

At this point, I can only offer condolences.

The white patches are likely to be a fungal or bacterial infections. Live fish will develop these infections when a stressor is introduced. As mentioned, aged fish are more suceptable.

Remove the stressor first. Your water got pretty hot if it was in the upper 80s. The water at the surface can easily get that hot, but if the water 18" down gets that hot... Your pushing your luck. When the water at 18" down starts to get in the 80s, I start shifting my aeration to night time only. I can do this because my system can still turn the pond over at least once in a 5 hour run time. Running at night helps to keep the water temps down. One diffuser in a half acre pond may have trouble doing this... Your system is probably too small for nighttime only aeration, but it should be looked into to verify. How hot did the main body of water get?

A massive influx of water could be a stressor, but for a month to go by lessens the likelihood that it was the main cause. Although, it is possible for the infections to have started then and added stressors influenced the fish's demise.

The numbers of deaths you mentioned don't sound horrible and, I agree that they looked to be aged fish, if not a little under weight too.

Do your research on a salt application. I believe that to be a good action to take, but not one you want to perform on a regular basis.

Did you ever figure out what the white patches were and how or did you treat the pond?

My condolences, AL64. I had a major fishkill in one (of two) ponds last week as well.

FWIW, I have previously fed BG (and CC) quite successfully on Purina Game Fish Chow. I currently feed a mix of Purina Aquamax 500 & 600, as I am now also feeding YP.