supplies, food, decor, etc. can be purchased from petsmart. they have a good selection. i haven't been to petco, so i wouldn't know, but try to look there too. walmart doesn't have many things, so i wouldn't recommend there.
be sure to do your research about food, water conditioner, and the like. most things specified for bettas are usually more expensive and detrimental. but, betta pellets are usually fine, just look for good ingredients and don't follow the directions on the bottle. be sure to get soft decor so as to not harm your betta's fins. (:
The food you will want to make sure meat/fish is the first ingredient. Pellets are the best staple, with frozen foods are the best.
I spent far too much time on that site last night until about 1am, which has set the expections pretty high. Reading the stories about transshipping (or even local shipping) has me trying to find something local first, if not I'll probably put a serious hunt on using that site. Seems like shipping is more than the fish in some cases.
Is a 28g tank too big for a single Beta? Any issues using one of the NanoCubes?
Sorry to ask so many questions, but I've been reading a ton and haven't seen an answer.
Nothing wrong with that size of a tank for a betta, that is a palace! lol..
The things you want to remember though with using larger tanks, is that some male bettas can have a hard time swimming in larger spaces, at first, until they build up their muscles. Most live their lives prior to you picking them up at a store in half gallons or less. So you will want to make sure your filter is on the lowest setting, or baffled by that way, or using another aquarium sponge in the outflow to help cause less of a current. But in that size of a tank, it shouldn't be too big of a problem as long as he has a lot of surface space that isn't being moved around. You will want to make sure that it is densely planted with medium to tall plants and a hiding spot or two such as a cave. It will help keep his stress levels down some from being in a larger tank.
A tank that size he would be good with other peaceful fish, a group of 5-6 cory cats would be awesome cleaners, and since they are bottom dwellers, your betta won't have an issue with them. Platties, female mollies, guppies are good with them. A tank that size you shouldn't have a problem with the smaller grouping fish such as the different tetras as they are usually mid level. Sometimes in smaller tanks, the small fast fish can fluster and stress out a betta, but a larger tank like that I would imagine they will be fine. But adding in tank mates is your choice, of course =) Just make sure they are mid-lower level swimmers, because others, like gurami's are top dwelling and territorial and will fight with your betta. They are bullies :P
You could also consider doing a DIY dividers and have quite a few in there. Just make sure there is a few inches from the water level to the top of the divider so they won't jump over.
As far as the Nano goes.. I think a member on here has one for his, but other then that, I have no personal knowledge of them.