Is tank too small?

I went to Petco and had the "expert" there help me put together an aquarium. With his help I purchased a 5 gallon aquarium with a filter system, 2 2 inch Golfish, 1 3/4 inch goldfish, & 2 algae eaters about 1 inch each. I have an air pump hooked to a decoration in the tank and used jugged distilled water to fill the tank. Now everyone on here is saying I have too many fish and that my algae eaters will starve. Petco boy said they would eat what the goldfish do. Who's right?