Question
QUESTION: i have 6 goldfish feeder fish and 1 fan tail goldfish in my pond its getting close to winter and i know my fish will start slowing down and i am thinking about moving my fan tail back inside because he is the slowest and the other fish stay in their group and i feel bad i don't want them to freeze to death but i know they are cold blooded my tank is 25 gallons and had 1 snail 1 pleo (sucker fish/algae eater) and 1 neon tetra if i move my fan tail (nilla) inside i am going to get a divider so she wont eat my tetra nilla isn't very big I've only had her for about a year and is one of the only fish i raised in my tank before putting her in my pond sorry i didn't include this earlier but we think our pond is about 600 gallons but since it is underground and is very detailed we cannot know for sure since it was here when we moved here in my pond we have live plants but in my tank we have plastic please can you tell me if they will be ok in the pond over winter or if i need to make arrangements for a bigger tank or if they should be moved especially nilla. sorry for the lack or punctuation and capitals I'm in a rush. thank you for your help,
Christine

ANSWER: You would need a larger aquarium for those fish.  You would want to use water from the pond (not fresh tap water) and cut a chunk of your filtration pad and place it in the aquarium's filter.  This will help seed a bacterial colony.  If your pond is deep enough (determine this by referring to your region's freezing table data, and add 4") these fish should be fine during the winter as long as you keep the entire surface from freezing over.  The fantail, in particular, is more susceptible to cold-water death.  Fish prefer live plants but it doesn't really affect their health to be around plastic ones.

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QUESTION: i cannot get another aquarium anymore will my fan tail be ok i can get my pond to not freeze over completely but if i put only my fan tail in my tank with the pond water will my snail, pleo, and tetra be ok? otherwise i will just leave my fantail in the pond

Answer
I'd say your best choice was to move only the fantail inside, into the tropical aquarium, still using a divider.  This way you can be sure that the fish doesn't do poorly over the winter.  You could try keeping it outside, but you never know what may happen.  Theoretically, they can handle the winter, but their mutations sometimes reduce their ability to take the cold.