You can't really cycle a tank that small, from what I've been told. I get it in my tank with Portal Prime after a day or so, but I do 100% water changes every 3 days so I don't really think it's a problem.
The tank is small enough for just a betta. 3 guppies added into that is very dangerous, since bettas are known to attack them. You would have to be doing water changes everyday because of the ammonia build up, and that alone can stress them all out :o
~Transformers Is My Twilight~Betta: EVOLUTIOOOON *jumps out of tank*
Portal Prime - HMDT
-.-Dreaming of Koi-colored DTs-.-