While there are exceptions to every rule, I will practically guarantee you, you will lose most if not all of the other fish in your tank to your Jewel. They are beautiful but IMO/E are only suitable for species tanks for the most part, definitley not a good addition to a community tank. I had a 2"-ish Jewel in a 38 gal with some danios and a breeding pair of kribs/their fry. I figured, hey, the danios can outswim him and the kribs can be nasty little guys in their own right, so I shouldn't have a problem.. Very wrong. For the first few days things were fine as he settled in, however, I quickly lost two of the danios to him. I removed the survivors to another tank and things were fine with the kribs when their fry were very young. However, the older and more indepedent the offspring became, the more relaxed the parents were, and after about 1-2 months in the tank, the Jewel had wiped out all the fry and beat the crap out of my female krib (who died after I moved the Jewel out, and I am still convinced it was from the stress of it all). Once I moved him to his own tank, the gorgeous colours he showed in the 38 gal became washed out, and he became extremely skittish - this from a fish who I used to hand feed! I would have done a species tank myself, but just didn't have the room, so I sadly made the decision to trade him in at the LFS in hopes of finding a happier situation for him.
Again, all this fuss caused by a 2" fish.. These guys can, and should, get up to 6". So not only is a 20gL tight quarters for an individual, add in all those other fish (especially those tasty little cherry barbs) and it is really far from an ideal situation for any of the fish involved.