My goldfish is sick?

Sounds like a bacterial infection. Clean up the water and get medication to treat. Watch the other fish for similar signs and behavior.

Tank size?

Filter size?

Size of the goldfish?

Last time you changed water?

Last time you cleaned the filter?

Do you condition the water?

Do you have a water testing kit?

How much water do you change at once?

Tank Size:

The goldfish would ideally have a 40 gallon tank for two goldfish.

However, you should be fine with at least 3 gallons per inch of goldfish.

If both of your goldfish are 4 inches long then you'd need at least 24 gallons of water.

Filter size:

Goldfish need large filters. More importantly, though, they do need a filter. The filter is home to many of the beneficial bacteria. That bacteria will actually eat the fish's waste (called ammonia). It then gives off another toxin called nitrite. This nitrite is eaten by another species of bacteria that grows in the filter. Nitrate is then produced.

In addition, the filter can help keep the water temperature from changing. If you have a light on the tank but no filter then often the top of the water will be noticeably warmer than the water on bottom. That's not good for fish, who require a water temperature that doesn't change.

Goldfish size:

This is important for me to figure out if your tank is too small or not.

Last time you changed water:

Sometimes illnesses are caused by a sudden change in water parameters.

Sometimes illnesses are caused by a gradual increase in the waste in the tank.

Last time you changed filter:

Remember, bacteria grows in the filter. That makes changing the filter a bad idea. I only rinse mine out when they clog (which isn't very often, by the way. My goldfish tank's filter has never had an issue at all). I know the box says to change the insert every month, but that's only because the carbon in the filter is used up after that time. You don't need carbon so there's no reason to waste money.

Conditioning the water:

This is important because chlorine kills bacteria. It's also very harmful to your fish.

Water testing:

Always very important to do once a week and whenever a fish seems off. It tells you the ammonia (fish waste) levels of the tank, the nitrite levels, the nitrate levels, and the pH. Liquid testing kits are far more accurate than strips. You can get more testing kits than that, but those four are the most important. Safe levels are: 0ppm ammonia, 0ppm nitrite, under 20ppm nitrate, and a pH that matches the pH of your tap. ppm stands for parts per million. If the readings do not show up in the safe level zone then do a water change. But not all of the water, remember.

How much water to change?

Well, if you do it once a week without fail then you can get away with up to a 80% water change.

If you skip weeks then you should keep your changes under 40%.

I do 60% changes on my goldfish tank and I do them every week.

Why? Remember; pH changes can occur the longer the water has been sitting around.

Don't take the fish out to clean the tank!

....

What about your issue now?

Now that you know what's wrong with your habitat for your fish (if anything) let's move on to the cause.

Bloating: Either infection or overfeeding. Most commonly over feeding.

Red gills: Ammonia poisoning, parasites, or infection.

Bulging eyes: Could be "pop eye" which is caused by bad water quality.

First:

Test the tank's water to make sure it is good.

Next:

Withhold all food for now.

Then:

Look up "Common Aquarium Diseases" and try to match yours up with one and get medication into the tank.