As someone who picked senegals for biological and evolutionarily cool reasons, I love this thread. I keep senegals myself...with geophagus. Yours are apparently all young. The polys will be probably active but chill, the geos I have learned to distrust but work around cause they are amazing too. Literally I've had 2 crops of Geo's that all started losing it on each other at about 6 inches. Try Synodontis petricola (or related dwaf synos) and I have had the best of luck with a SINGLE Mesonauta festivus. It literally bites the faces of bichirs that get too close and as a single fish isn't horrible, bit is kind of a jerk to any passive fish. Strangely, as target fish, large platys. Most are alive, takin hits and doing their silly breeding thing. Anything that lives past 48 hours will do fine with bichirs, be it feeder or high end fish. If they live through about 48 hours with senegals, they get ignored past that.
Christ I can't emphasize strongly enough what an amazing endeavour you have here. It's like all my dreams were fed steroids and then I got to see them. Then I shat the bed.