Wivell:
Your question is hard to answer until you know the flow of the spring to keep the pond full. If you have 1 gallon going in you are going to need to have 1 gallon going out plus drainage. I would be glad to discuss this with you. You can call my office at 1.800.822.3478 or email me at: [email protected] and Sheri will assist you in contacting me.
Otto