Hi Everybody, I'm not new to fish keeping in general, I used to keep a 70 gallon tank which lasted for 7 years until the fish were wiped out

. I stopped keeping fish for a while after that - I think I might have gone wrong with it somewhere. Anyway I am returning to fish keeping again, this time with a considerably smaller tank (I have less space than before) and I'm just going to be lurking around and asking a few questions so that I can figure which size tank to buy (the unit won't hold anything to heavy) and which fish will be suitable for it, and hopefully I will be here a while after that so I can learn a little and stop a repeat from last time. I'm going to be keeping cold water fish. I don't want my fish to be to cramped, so I'm probably going to keep a small species.
If anybody would like to give me some suggestions I would be very grateful. (oh, my size limitations are roughly 80cm length x 50cm depth x 60 height, judging from my hamsters cage of that size on a similar unit, but I'm not sure that the unit would hold that much water as it's made of a strengthened glass)