Are you putting them in your 30G? Is it 36" long? If so, it should work.
I'd add the cories first and let them get established.
Pictus can get a bit rowdy with each other, so I'd get only one.
For corydora, go with 5 or 6 of the same species.
Don't get the pigmy corydora. Pictus
are catfish which means opportunistic eaters.
Pigmy cory are cats too, but stay very small and could fall prey to the pictus.
Provide cover for them to rest in/under, using things like slate leaning against the tank back, caves and/or
driftwood.
If you give the corydora a chance to get settled in first, then it
should be ok in your 30G.
Different fish have different temperaments, so be ready with an alternative plan.
Ask the
LFS,
before you buy him , if they will take the pictus back ifn case he turns out to be a problem.
hope this helps,
alicem