I've upped some photos of the fish from my cool tank and a picture of the tank. The plant is java moss and decor is bogwood. I use only a Fluval 2 internal filter and no heater. The fish feed well and are always showing good colour and breeding activity so i guess something must be working well. I change about a 1/4 of the tank water every month. I feed tubiflex, daphnia and dry food. I use dry about 4 days, live 2 days and fast them 1 day a week. The temp ranges from 65F to 80F in the summer.
Hi, I've got an unheated coolwater tank. Temprature at this time of year is between 64F & 70F. It has been running for about 15 months without any problems. The fishes I have are 2 Ruby Barbs, 3 Golden Barbs, 4 WCMMs, 2 Black Banded Sunfish and 3 Bronze Corydoras. I will be moving the sunfish to a species tank with 3 others soon to try and breed them. I wouldn't recommend a cool tank if your room temprature would drop the tank water below 65f, well not with tropical species. I have known people to keep Platys and guppies down quite cool also. I wouldn't just buy fish from a tropical heated tank and pop them into a cool tank either. I think you would be asking for trouble.
There are a few fish that look great in a cold tank that will go down to the 50s like the European Bitterling (Rhodeus sericeus). There are a few other bitterling types available now and again which are quite colourful during their breeding season, they are usally marked up as Rose Bitterling. Then there are our native species like the Sticklebacks, Millars Thumbs and Minnows, these can be quite interesting to keep. You used to be able to get a lot of North American species suitable for the aqurium like, Fathead Minnows and Rosy Dace but I haven't seen them for sale in ages. Another you might consider is the Medaka or Ricefish (Oryzias latipes) It has a facinating breeding system and will go down to quite cool tempratures.
Glad you got the feeding sorted. I also sometimes tie a cooked prawn squeezed between my fingers on to a piece of cotton and dangle in the tank. Most small fish go mad picking at it, it's quite entertaining to watch them.
No, I was thinking what you would like to be? But, what would you like to keep is a better idea so I'll start you all off.
I would love a 8ftx2ftx2ft tank with large peices of bog wood covered in java moss, slightly tanning the water, very dark gravel/sand base lots of plants with lots of school of tetras, about 40 per school. 30ish corydoras and a few other south american speices that I would need to think a bit harder about. I'll let you know a bit later after some thought.