Bottom drain?

[Christi]

I built what I originally intended to be a goldfish pond in my back yard. It's about six weeks old now. It's about 2000 gallons.

I did not put in a bottom drain. But now I am wishing I could put koi in the pond. I read some places that bottom drains are essential for koi, and other places it simply says they are "recommended."

I have also read that some vendors sell "above the liner" kits to allow filtration similar to a bottom drain.

I don't want to buy a bunch of expensive koi and kill them!

Is there some kind of filter that I could get that would be close in quality to a bottom drain?

Or should I just forget the whole koi idea and stick with goldfish?

Thanks,

Christi