Small flies

[tedshoeness]

I have a 3000 gallon koi pond in my garden the purity of which is maintained by a very large below ground level filter system. The pit which contains this is about 7' square and four feet deep. Because one of the water valves leaks a little there is always about two inches of water in the bottom. My problem is that my garden is infested with very small flies which dance in small clouds throughout the garden, and also seem to be concentrated close to the pond. Cold weather does not seem to cull them because they remain throughout the Winter when they also come into the house. I do not have the means to take a photograph of a specimen because they are so small. Is it possible to identify from the above, and perhaps suggest how I can eradicate them bearing in mind that I must be careful because of the fish.

Tedshoeness.

PS. I have thought about repairing the leaking valve, but that is a major job.

[~T~]

Fungus gnat/scarid flies maybe?

[tedshoeness]

Thanks ~T~. It's food for research in those directions. Ted.