The guy at the petco here was "no" help and yes I agree so sad that so many people assume small tanks are wonderful to keep bettas in. I used to be one of those people :) Today my parents got me a 10 gallon tank from walmart with all the hookups for a late birthday present. I am obviously not using the filter and instead am changing the water once weekly like I do with my other bettas. I fell in love with a baby betta after losing my oldest fish to dropsy or some sort of horrible disease (after I nursed him back to health with aquarium salt and betafix) it was awful. I was in grieving and then went to the store with my husband who is also a sucker for cute bettas. When I went online to do research on my baby betta I learned about tanks and such. I felt so bad and somewhat responsible for my older bettas death but now have vowed to do as much as I can to help my betta family.
Today I was curious how my husband's betta would react to having the baby close by in another tank. To my suprise my "baby" flared and I saw his little beard come out. I know now that my betta is a boy so I named him Puddles :) My husband's betta Charlie is so silly for feeling threatened by such a small fish. Don't worry it was a split second and they were safe in 2 separate tanks.
I can't wait to get the divider for my 10 gallon but for now Charlie gets to enjoy it while Puddles enjoys his small tank with his heater. I am praying Puddles grows up healthy and nice :)