Water temp: 25 C; Tank: 20 gallons, cycled for 1month then added 1 platy, added the goldfish 1 week after. Added 2 nerite snails 2 days ago; last water change 40% was 2 days ago; used anti chlorine before adding the water then added seachem stability; no medication; no frayed fins or white spots. The fish is active and eats well, fed 2x a day 2 pinches of saki hikari per fish.
Help my oranda goldfish started showing black colouration under its head. I'm not sure if this is normal or should I start treating it for black smudges. 20 gallons tank, 2 oranda goldfish, 1 platy and 2 nerite snails, tanks is cycled, 40% water change every week, saki hikari is their main diet and some spinach, I dont know the ammonia levels since I dont have a test kit. Fish is still active and eating.