AusBonsai

Hi guys, bonsai Newbie here.
I don’t know what sort of plant this is, but it’s grown over a rock, and has water in the base, it was going well for quite awhile, but I moved it to a different room and within a couple of weeks the leaves have gone from a deep breath green to a pale green, sometimes yellow and it’s dropping many leaves. I have moved it back to its previous spot but I’m still concerned I have damaged it. Any suggestions for what might’ve been the reason and what I can do to return it to health would be greatly appreciated??

Your bonsai is a dwarf umbrella tree - Schefflera.
One of the most common causes of yellow leaves is keeping the roots too wet.
They can cope with indoor conditions but not enough light can also cause yellow leaves. A good place for it would be close to a large window but without direct sun on the leaves..
Another possible cause for yellow leaves is lack of nutrients. Plants can starve just as other living things. Most bonsai growers fertilise our bonsai regularly

Without more background it is really hard to pin down a definite cause for yellow leaves.
Some things that may help get closer to an answer -
Location: Often it helps know what part of Aust you are in.
More about how you care for the tree - how much light/sun it gets, how often you feed it, how long you've had it, how often it gets water, etc.