1/2 Barrel - gravel and plants question

Hi, I did more reading on plants, I have decided my "pond" is too small
and I will just leave the bottom bare as you suggested, just plants in
small herb pots for now. And keep the gravel to a minimum

What do you think if I just anchor the plant with gravel in pots and
soil in the tank at all? I think a bit of soil might likely cause a
big mess in my barrel, with the fountain pump running and small volume
of water, etc.

I was thinking water lily because I havn't got a floating plant of any
kind yet (but will continue to look for stores with hyacinth)
The pond get 6 hours of sun now and I think it will be too warm for
fish at certain hours without shading the surface quite well. And I
really want fish, even though can only support a couple of them.

BTW, any bigger pond is out of the question right now until I make this
barrel rather attractive, before approval for in-ground project will be
granted.

Next I have been wondering something else. If I add a small aquarium
filter to hang on there, would I be able to support more fishes?