Pump size for CIP system.

I am looking to build a CIP system for my 22 gal fermenters. I am also considering a keg cleaner similar to the one recently featured.
I would like to use a pond pump for cost reasons. I’m looking at options and GPH vary greatly. Any advice on pump volume for a system like this?  I’m looking at a 500 GPH model but perhaps this is excessive or insufficient.

I have to make something simply because cleaning has become a real hassle and one of the big reasons I am not brewing much today.
Thanks.

Commercial rule is 40 GPM and 20psi.