Family goldfish approx 7 years old and last one of three fish has been thriving muddling along despite my horrendous fish sins. When he got a fungally white spot of his nose DS and DH went to local pond/fish retailers who gave very helpful advice and I looked in this section, which horrified me (regarding my fish husbandry). I used to empty and scrub his tank,stones and tank toys; gave up treating the water in 2007 when I lost the stuff; NO FILTER 
.In my defence he lives in the hall where we can all see him and he gets good light, but he did just rattle along.Lovely gold colour,lovely tail, been on his own for about 5 years. White spot healed and he got his own back by noisily moving his stones all night!!