Hey LineDropper!
I think that you have little to worry about with keeping tiger barbs and quite a few, if not most, cichlids...so I would be more concerned with finding the right species of cichlid(s) that will not outgrow a 30 gallon tank. My reason for saying that is because, in the past, I have kept tiger barbs to act as dither fish in my cichlid tanks...and at one time, kept them with some of the most aggressive mbuna without problems. Additionally, I am currently keeping 10 Arulius Barbs and four Odessa Barbs in the same tank as almost a dozen P. Saulosi and have experienced absolutely no problems from doing so. However, I don't mean to imply that any community fish can coexist with any cichlid, but if you choose fish wisely, it can be done. The trick to doing so though is that the community fish need to be an appropriate size, quick swimmers, and probably a fish which schools/shoals; among other things. In fact, tiger barbs may be one of the best examples of a good dither fish for a cichlid tank...and IME, keeping dither fish in a cichlid tank has quite a few advantages to it, including making all of the fish more active and reducing the problems associated with aggressive fish.
Personally, I would advise against keeping 6 tiger barbs in a 10 gallon tank. While it is true that they grow to about three or four inches in length, they are relatively 'round' fish (sort of like a discus I suppose) - making them a bit larger than we might think. Besides, while you may experience less fin nipping from your tiger barbs because you have six of them in the same tank, keeping tiger barbs and other fish with similar nipping habits in a small tank may only make that habit more of a problem.
