I did the 10 gallon route when I had a couple goldfish. Don't forget that water weighs 8 pounds a gallon! So, with water in it, even a 10 gallon tank weighs a zillion pounds (cleaning it can be obnoxious). I would try the 10 and get 3-5 fish myself. I only had 2 goldfish but one died. I also had a cat at the time and even with a screen over the top, the cat managed to pull down the framed picture I had on that wall and break it, etc. trying to get to the fish.

Do you know where you'll put it? That makes a difference. When we moved into our house, the only place I really had for the tank was in the basement! I thought that was dumb (even though it was a finished basement) since we didn't go down there very much. I couldn't see cleaning the tank and feeding, etc. when I wouldn't be enjoying them much. So, we took the remaining fish to a pond and "released" it into the wild. Fishing, I immediately caught a sunfish almost smaller than the goldfish I'd just released! I knew then that "DD" would be fine in the pond.

S/he'd come from a County fair, I had had my husband toss quarters into fish bowls to win it, it only cost $5 or so (much more than at the pet store :-) and since he'd won it for me (he didn't want fish because he didn't want filters or other "noisy" equipment in the living room of our apartment, he can't stand equipment noises like that) I asked him to name it. He told me "DD" and I asked why that name (thinking it was "Dee Dee" short for Denise or something) and he explained it stood for "Dead Duck" as his sons had had goldfish before and they'd always died immediately. Since I wasn't "allowed" a filter he figured this fish wouldn't make it either but I'd had goldfish before too and never had any problem with them. DD thrived and grew in the 3-5 years we had him/her. Was a very happy fish. That's why I got a silver and black goldfish-type (DD was just a regular orangish goldfish) whom I named "Blackie" but I think DD killed it. I don't know what happened.

But guppies and goldfish, etc. don't need filters or anything, maybe some plants and a snail or two (I never had any luck with the snails?) to help keep it clean and oxygenated? But I would go with a smaller tank first and see how that goes and then graduate up if you like that and get into it, etc. I think larger than about 10 you're going to want oxygenators, filters, heaters, and a whole lot more "hardware" and stuff and it will be harder to clean and you'll have to really be into it. But I just had the 3 gallon bowl with the 2 fish in it in the apartment to start with so I'm sure you can do 5-6 easy with the 10 gallon?