I've posted this in previous threads, but here is my successful goldfish (coldwater) tank. Please bear in mind that many of my non-goldfish are still very small (i.e. the plecos and denison's barbs) and that my tank is due for an upgrade soon. As for the goldfish, I got them all at the 1" to 2" size and they're thriving

As for the non-goldfish, the Denison's barbs are new, the plecos are all about 6 months in the tank, and I've had all the rest of the fish for at least a year in these conditions. Three of the bronze corys are unintentional and exceptionally lucky offspring of one of the original inhabitants who is still in the tank.
1 9" shubunkin
2 6" orandas
1 5" celestial
1 4" moor
5 golden barbs
some zebra fish (they're getting slowly eaten, probably by one of the orandas, and are being phased out)
4 denison's barbs/roseline sharks
3 rubberlip plecos
1 royal pleco
1 ancistrus sp.
1 common pleco
2 peppered corys
6 bronze corys
3 dojo loaches
4 apple snails
2 ramshorn snails
no live plants
75g
fluval 404
aquaclear 100
twin tube fluorescent lighting
no heaters
1 powerhead
bubble wand
50% water changes weekly.