I have one divided 10 gallon that works very well it has a filter and heater. I have several smaller bowls from 1 to 2 gallon and I have one 5 gallon. The one that takes the least amount of work seems to be the 10 gallon one 30 to 50 percent water change a week. The others are daily partial water changes then once a month 100% water change, they aren't filtered. They are all cycled. I keep my home at a pretty even temperature so I don't really worry about heaters ,the one in the 10 gallon hasn't even been plugged in yet and probably won't be. The thing with a divided tank if the fish can see each other through the divider even if it is just a shadow mine will flare. I have a lot of floating plants in my 10 gallon so the fish can't jump the divider. I prefer glass over acrylic because the fish can't see a reflection of themselves. I just started cycling a 2.5 gallon this weekend that has a filter I am waiting for the nitrate spike before I put a betta in. I used some filter media from another tank so it might not spike but I don't want to take a chance. If you decide on a filter make sure you can control the flow or at least beable to block it to slow it down. No matter what size you decide keep an eye out for ammonia, nitrates and ph (some cities buffer their water and the ph changes as the water sets).
