You have a few months so it's not imperative you upgrade tank size yet ... a 20gal affords you more time than if you had a 10gal. Although they'll only get to about 2inches(maybe 3 in some cases), it's their activity level that requires a larger tank, with plenty of open space for swimming with plants, DW, rocks along the back and sides.
Also, a nasty aspect of TB's (aside from the fin-nipping) is their bullying of the smallest member of the shoal as they mature. Often the runt of the litter gets it's fins nipped, will hide and if the bullying is bad enough get stressed out which could make it prone to illness. Just something to keep an eye out ... it's why I had to remove a Male Albino from my main tank and put it in my son's
75g Planted Barbs Denison, BlackRuby, Tiger, Albino Tiger, Green Tiger, Cherry, Gold, Checkered, Odessa.
NonBarbs Cardinal, Neon, RummyNose, Bloodfin Tetras, Z. Danios. 1RTS. Amano, Bamboo, Ghost & RCS. 20g Long Shrimp Tank RCS, Tiger, Amano.