Baby cooter and baby map turtle?

i got a baby cooter rite now and im lookin into buyin my frinds baby map turtle off him and i was wondering would they end up fighting or would there be a problem with me puttin them together but like i got a 35 gallon tank rite now just till they grow bigger probly get a new one in a year would there be enough room in there for them rite now i got about 15 gallons of water in there half the tank. with a 55 gallon fluvual filter and a water heater and basking lamp.