i went for black gravel
really?? theres loads on the market. i see one for 1.3l

S i wouldnt put it in that small but i thought just for 1 betta that size would be ok

was gonna add a shrimp n 2 or 3 black tetras. i want the tank really to breed them.....
5.5L really is an incredibly small amount of water. Some bettas prefer small spaces, but I think that even that little is slightly extreme.
The 1.3L is very silly. I can't even see any fish would be happy in that!

If you did really want a betta in there, you couldn't put any other fish in there. Not only would more fish over stock it, but I would think that the betta would be pretty angry with the other fish, since he would be very territorial over such a small space.
Also, black tetras get far, far too big for 5 litres and need to be kept in shoals of at least 6 to be kept happy.
Another factor to think of is that for breeding, you need to have hundreds of jars for each of the fry, and the parents don't cohabit. The female is conditioned for a few weeks by putting her next to the male, then put in to breed. I'm not really sure on any of the details since I've never bred myself, but it's a lot of hard work, and a small 5.5L just wouldn't fit the job.
Something like this would be good for a betta (
link), and maybe a few shrimp. It would be good if it had a lid also, as bettas have been known to jump out. D;