Gallons/litres is ambiguous, what matters are DIMENSIONS, particularly length and width. Minimum size for adult for life would be 72"L x 36"W x 20"D (187 UK Gallons/ 853 Litres). To RAISE a juvenile, again it depend on the configuartion of your 50 gallons, hopefully it's a good length and width, depth not being critical, but if it's say 48"L x 15"W x 18"D I'd say for both physical space AND volume of water to tolerate waste, up to around 14" maximum.
If your thinking about your space and your pocket,I think it would be enough for a single specimen,but it wouldn't reach its max size,The biggest aquarium would make anyfish happy and reach its full potential,always pick the biggest possible tank..heres a photo if a striata ,I think one of the biggest striata Ive seen so far