Hi Mavis, how are you? I guess I see how the pecking order in your family works, hehe... oh well, back down to the 10gal for you <img src="/images/graemlins/smile.gif" alt="" />
I would say that your 10gal is pretty much to capacity, mostly because you are in the process of moving all your fish. It's not a good idea to be adding new fish to a system that's undergoing a lot of change to it, and if you take all the stuff out of the 15 to put in the 10, that's a big change as far as the animals are concerned. Give it a few weeks and see if you get any ammonia spikes. Try and run the same filter and don't rinse out the gravel or sand, so that you retain much of the same bacteria. If the tank stabilizes after a month or two with no deaths or problems, I would say you could get away with maybe a pair of platies/guppies, or something very quiet and small like a bumblebee goby (technically considered brackish, but they also do well in freshwater and are very hardy). But pushing a tank to its limits does make it a little bit riskier if you do get a disease from the new fish, so I personally think leaving it as is makes a delightful little tank. Good luck!