Air stone use?

My little 400gal pond has done wonderfully all summer long - crystal clear
water (after the spring bloom), lilies going crazy, fish thriving, including
a host of new babies. However, I was thinning the hyacinth this week and in
removing several plants noticed a subtle yet distinct odor that suggests
anaerobic activity. My little pump just causes a trickle of a waterfall, so
I don't think I'm getting the oxygenation that I should have. So, here's my
question:

I'm assuming air stones are the answer, as well as a larger pump. How and
what kind of air stones are to be used? Am I going to have to invest in
some kind of air pump as well?

TIA,

Fred
Oceanside CA