I have 5 small goldfish in a 5.5 gallon tank, with 3 snails, and a filter. Do I need to add an air pump too? Sometimes, my goldies come up and start gulping air. Is this okay? I also have another 3 gallon tank with 7 baby goldifsh less than an inch each. I plan on giving 3 away, so I'll be left with 4. I have a filter in my 3 gallon tank as well. Some of my fish come up for air too. Do I really need an air pump for both of them? What are the pros and cons about an air pump?:confused:

There are no cons concerning air pumps. They supply oxygen to the water that your goldfish need to survive.
Gulping at the surface of the water indicates that there is not enough oxygen in the water.

You must add the air stone for them to properly survive. They are not expensive.

When you overcrowd, as I think you are, you have a lower percentage of oxygen available to the fish in the water. Try and get you a larger tank and use a filteration system and be sure to have air stones in the tank for extra oxygen. Your fish will be happier and healthier.