1 gallon tank

Hello, my daughter recieved a goldfish in a one gallon tank. This
started my interest and we have just moved him into a 55g with 2
buddies and another to go in when the ammonia spike drops and I can see
that he is healthy. The 1 gallon tank had a little 15 watt bulb for
light. It recently blew and I bought another. I've noticed that the
tank water is getting quite hot. Somewhere between 78-81. I'm keeping
the light off during the day and only putting it on for a hour or so in
the evening when the room temp drops. Any day know the black moor in
there will go into the big tank.

My question is, could I keep some very small tropical fish in it. I
know it is very small but thought maybe 6 neon tetra's? Hate the
thought of a tank sitting empty. Once the gold fish get big it wont'
even work as a hospital tank.

Anyway, just a thought
Thanks
Mellie