You need a much larger tank than 20 gallons. I used to pull my koi and shubunkin in from my pond when it was small (400 gallons. Now at 1000 gallons, zone 7 I keep them out all winter long) and I would use a stock tank that held about 60 gallons of water. They were kept out in a non-heated enclosed porch - so I did have to also use a small heater (the temps in this porch wouldn't hit freezing, but it did dip down to the upper 30s in the dead of winter). You really should not be going anything smaller than 50 gallons for your fishload (since it's a temp situation I don't think you want to invest in something bigger) Stock tanks are great because you dont' have to worry about lugging a glass tank somewhere or storing it and not breaking it when you're not using it. Even if you use a very large rubbermaid bin or big big plastic garbage bin. Just hook up a GOOD filter to take care of the bioload of all those fish. 50 gallons is not really large enough to encompass all the fish you have, but if you pick up a filter that is rated for a larger amount of water you should be fine.

I also used to use a spare pond filter and hook it up to my inside set up for my koi.

Also make sure you cover the top. I found my fish tended to jump in the smaller space.

20 gallons is way too small for 7 goldfish of that size. Rule of thumb for goldfish is 10+ gallons per fish and minimum 30 gallon per fish ( the 30 gallon is because of the legnth gold fish need to swim back and forth). Goldfish also can live up to and +10 years, people reporting 20+ is not unheard of. When buying a fish tank you have to look at the potential adult size of the fish being kept. Assumeing that the 5 "goldfish" you mentioned are comets ( adult size +/- 12 ") and the 2 fancy tailed (+/- 8" adult size). You would need an awfully big aquarium to house them or a few smaller ones. Goldfish are poop machines and will need good filtration for the tank(s). For this winter I would suggest minimum a 55 Gallon with a filter rated up to 80 gallons or 400GPH.Depending on the ammount the fish grow over the winter and next summer you may need to seperate them into 2 tanks or get a larger one.An inside aquarium is sometimes more of an investment than a pond or equal to it. To save $$$ you can look in the classified adds and garage sales for used equiptment. A fair price for larger tanks (55 gallon +) is a $1US per gallon. A popular supplier in Canada, both online and store, is Big Al's, Also I think www.drsfostersmith.com delivers in CAN. If you are using filtration in you pond add as much as possible, if not all of the filter media to your inside filter. If your pond filtration allows you to remove it and install it inside the tank then that would be the best and less expensive plan. Also any rocks and decor that was in you outdoor pond that is appropriate for the aquarium will help. The reason for this is to maintain the nitrogen cycle that was established in the pond. Doesn't seem like you have much time considering your location.To help acclimate the fish when transfering them. Run the aquarium about 48 hours filled with water. Take a bucket and fill it aquarium water then dump it in the pond. Fill the bucket with pond water and dump it into the aquarium. Repeat this until you think you have exchanged 50% or more pond water to the aquarium. Transfer the fish to the new home. This is to equalize differences of water parameters (temperature, pH blah blah blah) from the pond to tank. I like to add new fish in the evening without any aquarium lighting, I also do not turn on the aquarium light for a day or 2. This is too limit stress from the move. Hope this helps and if I missed anything I'll add to it later.

I didn't mean "I don't turn on the light for a day or 2." Don't quite know why I wrote that , guess I was distracted LOL. Usually just overnight will do, but it wouldn't hurt either way. These are jusy my suggestions since you asked. It can be done several ways. This seems to cause less stress which is a key factor in fish transportation.

Another easy way to calculate what size tank you'll need is 2 gallons of water per inch of goldfish. The stock tank idea is great, and then get a really good filter for it. I have a 30 gallon tank in my house but the filter is for a 100 gallon tank. I used to keep my koi in there when they were much smaller.

With pond fish, as the water starts to cool down, in general they are less active, don't eat as much, and there will be less waste. If SilverFlower is bringing them inside and raising temps up above 75 degrees F, I'd definitely be more concerned about stress and waste. I transferred my pond fish in and out with the seasons for about 10 years without any major issues, nor major need to set up as carefully as I might with tropicals. I'd say the water temps with the set up in the enclosed porch never got higher than about 65 degrees F.

Goldfish are definitely adaptable to cold temps, fantails a little less so. If SilverFlower kept the temps low, the fish would probably transition more easily with less stress.

Are you sure your pond water is 68F? I am also in MB and my pond is probably 45 to 50F though itÂs in the shade so maybe that makes a difference. Anyways, I have already brought my fish inside.

The first winter I used a 30 gallon aquarium for two small koi and two tiny goldfish. The koi were only 3 inches or so. It worked okay. A good filter is recommended, lots of power, perhaps one with a biowheel like a penguin brand.

Last year, however, the koi had grown to about 5 inches so I knew that tank was too small. I bought a 44 gallon preform pond (from a place like home depot pond section) and propped it up on the basement floor with cinder blocks (it had a plant shelf that needed support underneath).

This year, the koi are hitting 7 inches, so I bought a 140 gallon stock tank. I had to go to a livestock equipment supplier to find one. They are usually used as feed or water troughs for livestock. Anyways, I filled the stock tank with pond water. Last year I used a pail, this year I put an adaptor on the pond pump and pumped it through a hose, down the basement stairs, and into the stock tank. If you catch and move the fish right away they are basically going into the same temperature/chemistry water as outside so less stress.

I have a homemade adams filter in the pond outside, so basically took a smaller pump and a Rubbermaid food storage container, and made a smaller version of that. I took the filter media from the outdoor adam filter (the lava rock and quilt batting, etc) and put it in the new filter.

Still, for the first month especially be sure to keep an eye on the water parameters (ammonia, nitrite, nitrate, buy test kits). No matter what, my levels always seem to go through an "adjustment". My ammonia level is sort of holding steady and in the safe range, but the nitrite is now spiking so IÂm doing water changes every two days. This can get frustrating, but if I recall from last year just when I was ready to pack it in things finished cycling and it was good all winter. Of course during winter I did water changes every 8 to 12 days and tried to get the crud off the pond bottom while doing so. Also, donÂt overfeed the fish especially for the first while until the tank cycles itself.

As for the fish still being outside, they can take cold water, but probably best to bring them in sometime in the next couple of weeks as you never know when winter will set it. One thing I learned is to keep an eye on them when the water outside gets cold. Their immune system is less resistant to disease at cooler temperatures. I had one fantail develop an infection/fungus and had to bring him inside, isolate him in his own tank, use medicine and anti-biotic food, etc. Fortunately, I caught it in time and he's recovered.