I sure hope they work, because I'm turning mine - which I've just been running as a water feature for the last 3 years - into a pond this spring. (Mine's circular, 5' diameter and 2' deep, about 275 gallons.) I'm going to make a 60 gallon DIY bog filter for it.
Yes, goldfish eat plants. But you can have plants anyway, and if you get the fish young enough, you might be able to even sneak a couple of lilies by them - while they are too young to see them as a tasty snack.
Ideally, you want some bunched plants to sink and floaters to cover at least 30% of the surface of the pond. Since I'm doing a bog filter, I'll also get to plant a bunch of hardy bog plants, too.
Comets, shubunkins and commons are what you want to put in there. Rescue some feeder fish from one of the big boxes.
Since my local sources for pond plants are very, very limited, I believe I'm going to order from
these folks.
I've already got the container for the bog filter, some of the pricier supplies and my pump. All together - plants included - I think I'll be able to do the bog filter for just under $300.
And then, it's off to rescue 6 or 8 fish...