My sister recently gave me a bonsai as a gift from her bonsai-savvy co-worker, no ID, no care instructions aside from "water frequently." She has been flaking out on asking her co-worker for more info for the last few weeks, and I'm in need of help. See pictures below. (I did not remove a rock it was growing around; it was given to me this way so I'm guessing it was grown in a pot and then transferred to this shallower one)
I just today noticed some leaves blackening at the tips/edges, and a couple yellowing (fell off when I was moving the plant to take pics). From what I've looked at online it seems like an over-watering problem. Hopefully from these closer leaf pictures an ID will be possible. Some new leaves have sprouted in the ~4 weeks since I've had it, so I thought I was doing the right thing, but clearly not.
I have this plant on my desk, in a corner adjacent to a window. Sunlight does not fall directly on the plant, but my room gets a reasonable amount of light, and is relatively warm these days. (Upper seventies in my room, I'm in Portland, OR) I have been watering it twice a day, with about half a cup of water each time. I also have a spray bottle that I spray the moss with, since when I watered it was tough to get all of the moss moist, which I assumed would help keep the moss from dying itself (still seems a bit crispier than it should be). Water almost never drips out the bottom, so I assumed that I wasn't overwatering. The soil underneath the moss has a good amount of that white foamy gravel stuff (whatever it is called https://i56.tinypic.com/2m3mwdx.jpg).
From these pics can anyone identify this bonsai? Watering method revisions? Sunlight exposure change maybe? First aid to help reduce further leaf loss (treatment for fungal something)? Should it not even be inside?
I don't want to kill my first bonsai! Thanks for the help.