At least 29 gallons! You can do filterless natural planted (Walstad-style) if you really need the silent aesthetic, but for crying out loud CHECK YOUR WATER PARAMETERS AND GET AN AIRSTONE STAT
…assuming that’s a fancy goldfish and not a common or pond comet, in which case all bets are off and you’re gonna need the mother of all tank setups or, better yet, a fucking pond
At least 29 gallons! You can do filterless natural planted (Walstad-style) if you really need the silent aesthetic, but for crying out loud CHECK YOUR WATER PARAMETERS AND GET AN AIRSTONE STAT
…assuming that’s a fancy goldfish and not a common or pond comet, in which case all bets are off and you’re gonna need the mother of all tank setups or, better yet, a fucking pond