i don't know why you would need a uv sterilizer, but aquarium uv sterilizers are built so that the light never leaves the unit. i don't know what you're looking at when you say, "would it be too bright," but i assume that you're talking about just the bulb, which would be very harmful.
as for the "carpet mini leaf grass," i'm assuming that you're talking about dwarf baby tears or something similar. are you certain that your lighting is adequate, do you use a co2 system, and use fertilizers? if the answer is no to any of those, i highly advise against dwarf tears (or most any other carpeting plant, either). i imagine that co2 injection would be impractical, expensive, and hard to find in malaysia, too, although i don't really know. just, my point is, as a beginner, stay away from carpeting plants.
the quarantine tank would need to be cycled.