Hi and welcome to the forum
The angelfish has a graze or wound on its side. It is not white spot and should heal up by itself if the water quality is good. However, you need to monitor the fish and see if any are attacking the angelfish.
What other fish are in the tank besides the angelfish and goldfish (possible koi carp)?
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The goldfish/ koi carp appears to have chemical burns. These appear as black patches over part or all of the body. it can be from ammonia, nitrite, overdosed medications, chemicals, etc.
Treatment is to check the water quality for ammonia, nitrite, nitrate and pH. And do a 75% water change and gravel clean the substrate any day there is an ammonia or nitrite reading above 0ppm, or a nitrate reading above 20ppm.
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How long has the aquarium been set up for?
How long have you had the fish?
What sort of filter is on the aquarium?
How often and how do you clean the filter?
How often are you doing water changes?
Do you gravel clean the substrate when you do a water change?
Do you dechlorinate the new water before adding it to the aquarium?
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How often are you feeding the fish?
Goldfish and angelfish require different types of food. Goldfish should have lots of plant matter in their diet, whereas angelfish are more meat eaters.
Temperature wise they should be ok together and seeing you are in California, there's not much you can do about the heat anyway so don't worry when people tell you to keep goldfish in cold water and the others in warm water. It ain't gonna happen where you live.
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Goldfish do prefer harder water with a higher pH than angelfish.
What is the GH (general hardness), KH (carbonate hardness) and pH of your water supply?
This information can usually be obtained from your water supply company's website or by telephoning them. If they can't help you, take a glass full of tap water to the local pet shop and get them to test it for you. Write the results down (in numbers) when they do the tests. And ask them what the results are in (eg: ppm, dGH, or something else).
Depending on what the GH of your water is, will determine what fish you should keep.
Angelfish, most tetras, barbs, Bettas, gouramis, rasbora, Corydoras and small species of suckermouth catfish all occur in soft water (GH below 150ppm) and a pH below 7.0.
Livebearers (guppies, platies, swordtails, mollies), rainbowfish and goldfish occur in medium hard water with a GH around 200-250ppm and a pH above 7.0.
If you have very hard water (GH above 300ppm) then look at African Rift Lake cichlids, or use distilled or reverse osmosis water to reduce the GH and keep fishes from softer water.