55 gallon is enough for a baby, the most important thing now is to keep the water pristine! No nitrit, ammonia, nitrat below 50 and ph around 6-8. Nice ray! You will have to upgrade within the next half year, if not even faster.. I had 2 hystrix pups in a 60 gallon for a few months, but moved them to a 180 gallon now since i got a little worried about the waterstability in sucha small tank.. I also have autodryp on my 180 gallon.
Read the stickies as said above, they are VERY helpfull.. I think i read them 100 times before i aquired my first ray, and has not yet lost one single ray.