What tank size would you recommend for the following fish?

[Naturepants9]

I have taken care of fish for years before, so I'm not a newbie... but only on a small scale. (I've never had anything bigger than a 5 gallon tank.) I want to "upgrade" and have the following:

3 goldfish (2 comets, 1 fantail)
3 mystery snails
3 zebra danios
a few java ferns

I know all that COULD live in a five-gallon tank for a while, but I don't want to just keep the goldfish alive "for a while". I want to be able to keep them alive and healthy for their true lifespan, 10 or more years. So. What size tank is the BEST for that? Also, what's the minimum size I could have to keep those healthy?
Actually, I did research, and zebra danios are hardy fish that can either go as cold water fish or tropical fish. My goldfish tank stays about 72 degrees, and I have read that that's a fine temperature for zebra danios.

 

[daprasi]

55 gallons, but how big are the snails?

 

[Alex B]

30-55 gallon tank would be just fine for those fish.

 

[Julia]

60 Gallons + for the goldfish and then it will need to get upgrades.

Zebra Danios are not cold water fish and would not survive with the goldfish for very long. They'll need at least 20 gallons.