Thanks!

That looks like an old galvanized wash tub. If so, you should probably think about taking the fish back or moving them to a suitable container. The zinc in the galvanized coating is poisonous to them. Fish are not supposed to be kept in galvanized containers.

http://www.about-goldfish.com/goldfish-dangers.html

It is also nonsense to suggest that goldfish don't need filters. All fish produce waste and that waste needs to be neutralized in order to keep the fish healthy. It is possible to keep fish healthy in a pond without a filter only so long as that pond is very lightly stocked and fed. In that case the bacteria that do the processing of fish waste are on all the underwater surfaces of the pond instead of the exposed surfaces within the filter. Add more fish and more food and you need more surface area for bacteria to colonize. That typically means a filter.

Thanks for all of the feedback!

When I was a teenager in the 1950's we had a fishpond. It was shallow, so my dad made a tank for the basement to keep the goldfish over winter. It was made of galvanized sheet metal. We saw no ill effects of spending 5-6 months, mostly in the dark, on the fish. We did this for 6 years with the same fish until I left home. We even had reproduction each summer. So, I don't worry about the zinc. Especially in an old tub.

Did you have hard alkaline water? Because if you had cold, hard, alkaline water and you didn't really feed the fish because it was winter, you would get away with it. However, if that water goes acidic from biological activity then Zn leaches into the water and all your fish die. Zinc poisoning from galvanized tanks is a well known problem in aquaculture.

We had hard water from the farm well. I have no idea about pH. Just that we had no problem.