Well, Russell, if he's a guy (we don't know yet) he may think his pond which is 6x3 is 8x4.

That could mean his water is 2 1/2 feet deep. Or it could mean the water is only 200 gallons, hard to say.
No matter what direction he turns he will need to learn quick- get a handle on just how much water he's got, just what he's going to do with winter, and where the poop is going to go. He has a chance to miniturize some very effective DIY filtration and be successful with the small pond until the situation improves.
Do you have any small systems left in your store?
Mickey the windowman