Hello and welcome to FF! Have no experience keeping CSFs; but most USA Rana sp. care is similar. Here is a care article for the Leopard Frog you can use as a guideline: Frog Forum - Leopard Frog Care - Rana pipiens (Schreber, 1782) and R. sphenocephala (1886). A 20L aquarium should work for frog all the way to adult size. Article recommends 50-50 land and water; but I prefer around 30-70 because Rana's love being in water.

Main thing is to use dechlorinated tap water; gut load crickets with carrots; lettuce and oats 24-48 hours before feeding the frog; and size insects (i.e. crickets or Dubia roaches) same as distance between frogs eyes. Food should be supplemented with reptile CA/D3 2X and vitamins 1X weekly on different days with skip day in between for a daily fed baby. A sample schedule would be: Mon & Fri CA/D3 and Wed Vitamins. If for a larger juvenile eating every other day, just space out the supplements to follow a similar rotation. Good luck and feel free to ask any questions !