Hi Sjbaby, I've often thought of creating an indoor pond. First off, how big of an outdoor pond are you creating. I will warn you that the pond hobby is catchy. You may be wishing you opted for a bigger pond. There are a few different types of ponds. The most popular are with a rubber liner. I have two ponds, my first is 2000 gallons, my second is 50000 gallons. As I said the hobby is catchy. A garden pond has rocks and gravel on the bottom and looks very much like a natural pond. A koi pond does not have anything on the bottom, with bottom drains and increased filtration.
Now not to intimidate you, if you are looking for a natural looking pond then go with a garden pond. Many people who are deep in the hobby will state that a gravel bottom is not the way to go. However if you just want a nice garden attraction with places to plant, the sounds of a waterfall, and the opportunity to plant aquatic plants, a garden pond is the way to go.
Both gold fish and koi are very hardy. My temperatures in the winter dip to below negative. For temperatures in the 30's, I would suggest to run your pond all year. The fish will hibernate for the winter, you will have to change their diet to a wheat germ as the weather gets colder. Stop feeding them when the water temp drops below 50. They will be fine.
Here are a few suggestions, build caves so the fish have a place to hide from the sun and predators. As far as predators, do not waste your money on fake props of animals, they don't work. Build your pond so it is difficult for predators to get your fish. Do not have shallow areas, these are areas that large birds of raccoons will wade. Buy what is called a Scarecrow. This is a devise that you hook up to your garden hose. It is motion activated to spray water in the area.

Hope this helps...here is some pictures of my ponds. I haven't done much with the big pond yet, it was just installed.

Craig

big pond

right now i am just thinking, but temps here get to 30 below, not 30f. i am not sure i am up to all the work to keep it up. but thank you for the info.

I learn from my mistakes. My small pond is only 2 feet deep. Also make sure your pond is at least 3 feet deep. As you can see, I have many shallow areas. This was my intervention after a predator attack.

I am in WV...got to -16 below here this year...pond stayed frozen for a month...I have some depth@3 feet...didn't put in a heater and should have...lost all the koi..but the goldfish lived...I will have a heater next winter...my pond is 12x24....7500 gallons...happy ponding! Dave in WV

Craig, That is one Bad@ss pond.....just sayin....nice!

TY Delaney...it was funny, my koi from the smaller pond looked so big until I transferred them into the big pond.