Can you put two goldfish in a bowl?

If you have an actual bowl and not an aquarium, then you would not want to be putting a lid on. Goldfish bowls have very small surface area for the water and that affects how much oxygen your fish can get. They actually aren't that good for them. Putting a lid on would reduce this even further. Aquariums can be covered with glass especially supplied, although it won't be a complete cover.