There are many people that use rubbermaid totes in breeding setups, or for holding fish. I don't think moving them to your smaller 10 gallon would make any better sense. They'll be fine in there as long as you are providing the care they need (& it seems like you are). You can pull that rock work out like others suggested for more space and ease of cleaning. But they can live in there no worries, until you get your pond. Personally, I think the big daily water changes are overkill, goldfish don't require stringently sanitary conditions. Just cut back to feeding once a day and a water change or 2 a week.