What makes me sad is that people that tend to buy products like this don't think of the fish as pet, friend and companion.. to them it's decoration that moves and eats.
I was at Petco about a year ago and saw this young mother with her two kids and they wanted a "nemo" so she got the SMALLEST kritter keeper they made and some fake stones.. and 2 bettas to go in each.. When the Petco employee was trying to explain the importance of keeping clean water (of course heated filtered, cycled wasn't mentioned) she wasn't listening.. There was nothing I could do.. poor fish.
I wish more people would do research, you can create a stunning underwater planted world with the Walstad method, from what I've read if it's done properly you won't need a filter at all. (I'd feel strange not using one). I've seen it done successfully in bowls, (big ones ~5 gallons) and that is easily heated..
It feels like an endless battle. :(