I just ordered one of those Lee's Triple Flow corner filters for my 10G betta tank. I need to replace the current filter because I just hate it. The tank right now has 1 betta and 2 mystery snails in it, but the snails are going to be relocated. The tank will only ever have the 1 betta in it after the snails move out. I think this should do a fine job with the added benefit of acting as a bubbler, so I will only need the one area of water disturbance instead of having a filter and a bubble stone. I was going to DIY it with a nalgene bottle and a bubble stone, but I'm lazy and this was $6.
So - filter media and order? I have at my disposal: activated carbon pellets (which I have never used just have on hand if the need should arise), Eheim Ehfilav - crushed lava rock, several thicknesses of sponges, and a large bag of filter floss. This filter has just one compartment, but I can layer things. Am I getting too fancy for a single betta tank? I could just do a layer of lava rock under a wad of filter floss, but it seems like I should be making a sandwich of some kind here.
This is the filter.
Amazon.com: Lee's Triple-Flow Corner Filter, Small: Pet Supplies