Doesn't look like ich to me
The malachite should have killed the parasite in the entire tank. More importantly, your tank needs lots of water changes, and it needs to CYCLE. Gravel is not a good choice for substrate, because it traps enormous amounts of poo and bacteria and leads to poor water quality over time. Regular playsand, washed thourougly in a bucket with a hose, would be a better choice. OFC you can use gravel with no problems, you just have to change 1/3 of the water religiously every week. Goldfish are pretty hardy once they have been established in a large established tank. You can even breed them fairly easily with a ten gallon tank and a mop spawn or you can even hand strip them. They can get huge and live for 20 years or more.Don't want to place any more fish in incase it was not ich, if it was a fungus or anything else would new fish catch it?
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