We've just gotten a small pond/water garden started. We were lucky enough to have had enough rain of late to get it filled without using tap water. It's kidney shaped about 15 feet long, 4 feet wide, 18 inches deep midpoint. No electricity run to it just because of the cost.
I've put in a few water lillies, floating planter, barley ball for cleaning and some underwater plantings. I introduced 10 common goldfish and 2 shubunkins yesterday. We're located in a semi rural area and hope the local critters don't decide to dine on the fish before they grow up.
This is our first foray into fish keeping and water gardening, but so far it's very enjoyable (after the initial dig). If anyone has ideas or tips on what to expect, what problems might arise, I'd love to hear them. I'm especially curious about the shubunkin if anyone knows. I haven't laid eyes on them since putting them in the water.
You'll want to use some kind of system to circulate the water. Nothing fancy, and it can be on a timer so it dosn't run 24/7. There are plenty of DIY "systems" on the innerwebs.
At 18" deep racoons (+ the birds) will get the fish, if they don't have somewhere to hide, usually a piece of pipe (clay) in the middle.
If you have too much sun you will get a bad alge bloom, and it'll choke out the whole pond.
Usually, like a salt water aquarium, it's best to let the pond "settle in" for a few weeks, so you can see how it's going to react to it's position in the yard (sunlight, plant coverage to control alge, etc).
Once it's balanced out then I would have added fish. You might be repalcing a few till then.
I studied the hell out of making a backyard pond and then said..........screw it.