Fish death....I have more questions

[sushi]

Well the EPA was here this morning and it looks like it wasnt mosquito spray.  Last night I went out with a flashlight and I had a bin with babies in it in my big pond.  Well I saw 1 baby about 1/2 inch long.  1 survivor...they told me babies would be the first to go.  I showed them the bottle of Deet and I need to call a toxicologist they gave me.  My question is...if it was a lack of oxygen situation, would that kill the string algae?  So now I'm thinking it couldnt be poison if i have a survivor.  I may never know 

[frogman3]

For whatever reason your string algae died the decomposing algae would use up oxygen in your pond. Depending on how much is decaying and your oxygen level prior to the algae dying would be a factor in or if it could be enough to kill your fish. How fast that would occur I can not say. At low oxygen levels and high water temperatures your fish are the most susceptible. The biggest go first. Koi before goldfish from what I have been told. I hope this helps. Tom

[Kittyzee]

Oh no sushi.  I am sure you want to know what killed your fish and at the same time the algae too.  I hope you find your answers for your peace of mind and also because of building your 'dream pond', you would want to know what to do or not to do to prevent this from happening again.  It may just be a combination of many things happening at the same time.   

[LeeAnne151]

I remember long ago on the Watergardening Magazine forum that someone went on vacation and teenagers poured bleach into their pond and killed all their koi. That would also kill the string algae and make it look pale. Is this a possibility?

[sushi]

At this point anything is possible. I just dont know.  The heat makes more sense, but I dont know if that would kill the algae,   I wouldnt think so

[karen J]

If it was anything that depleted O2 levels in the water, the big fish would be the first to go, so it would be normal to have babies or some smaller fish survive.