http://www.bioconlabs.com/nitribactfacts.html
"Nitrifying bacteria reproduce by binary division. Under optimal conditions, Nitrosomonas may double every 7 hours and Nitrobacter every 13 hours. More realistically, they will double every 15-20 hours. This is an extremely long time considering that heterotrophic bacteria can double in as short a time as 20 minutes. In the time that it takes a single Nitrosomonas cell to double in population, a single E. Coli bacterium would have produced a population exceeding 35 trillion cells."
The sparkling gouramis are very small and they don't eat much. They're kind picky...they like flake food crushed small but not too small. I think you'd be ok with them. But, since they will pair off. I'd get 4 and hope it worked out. I myself have 3 and wish I had 4 b/c one is always odd man out. If you get 4, I'd add them 2 at a time 2-3 days apart.
The panda, I'd add 1 at a time, 2-3 days apart. Cory eat a lot. They are always hungry so they make a bigger bio load.
After buying fish with VHS from my local fish store, I'd really recommend a minimum of 3 week QT. (Or at minimum a UV light in the tank.)
(Friend of Bill W., One day at a time)