4 more barbs... They look nice shoaling together...
Do you have a theme in mind? 30 inch wide tank, you can host a silver aro if you want to; or some larger cichlids...or a pair of convicts and how long it will take to fill up the rank with convict babies.
Thats nice tank at a good price! Im a pleco guy so I'd put some DW and bunch of plecos along with your barbs. And its definitely a glass, it still a very darn good deal
Those catfish are brackish water that eventually need full marine. You could try Pictus as an alternative though but then again if you are adding those I would find larger ones because smaller ones might get eaten by a larger fish potentially killing it.