I guess everyone is aware of what awaits a lot of the 25 cent "feeder goldfish". I'm wanting to start up a pond shortly specifically for Comets. I was originally planning on a koi pond, but after seeing Comets in unimaginable conditions at a local Petco, I decided I'd rather go with Comets. How many gallons should I have pet fish? I'm wanting a deeper pond rather than a wider one.