i encourage any new fish hobbist. it is fun and exciting. there is nothing wrong with a small tank. it can be a good educational start. just take it slow and really be certain what you would like to have in there because the space is limited. as for the platys, i would not put them in a small tank. they are messy and can be a little nippy with smaller fish. as for the cherry barbs, i have 8 of them in one of my 55 gal. tanks and they all swim together. quite nice, and very colorful. but i must say, if you added the cherry barbs,other than a couple of corys that's all i would add. you have to be careful in a small environment. small impacts can make big problems. i find it easier to maintain my big tanks than the 10 gal. good luck.