Red patch on goldfish

Lupin

Chloramine and heavy metals which most dechlorinators can easily removed.:)
Overnight is sufficient or you can try getting an airstone to aerate the water. Chlorine is a gas and should dissipate as soon as you do either of those above. I prefer dechlorinators as the method is almost instantaneous.:)

Lauren, welcome aboard.
Try API Master Freshwater test kit.:) It's easy to use and accurate.:)

Good luck and hope for the best.:)

Firebelly girrl

Hi well..when i put my 2 year old Goldfish in a 5 gallon (temporary) he got VERY red/brown right at the creases of his tails and fins and around his face, a 5 gallon is not for a Goldfish at all! And yours looks pretty large! Theres just not enough oxygen exchange for them, unless you have bubble stones and stuff. They are just to dirty of a fish too, i would try to find somebody who has a 10 gallon and give it to them, and get a betta, they will be perfect for a 5 gallon Sorry, but a Goldfish has needs =) lol