Your fish load is good and light. If you have all those solids, some
more effective filter medium or settling tank may be in order. Lava
rock is notorious for getting clogged and for not filtering. Folks
here will suggest many options.

That's kinda what I'm thinking. Any recommendations in particular?

The slow-passage veggie filter is always good. Ours take about 45 min
for the water to pass through. The hyacinth roots really slow the
flow and most of the junk settles out before the exit.

Do you set that up outside the main pond? Like, for instance, would I
put them in my waterfall box?

We have used a UV to handle initial algae blooms. Once the pond
plants really get going, however, we turn it off. It needed less than
2 weeks this year. Low use saves cost!

Good luck.

Jim

Oh that's good to know. I have been thinking about UV and wanting to
make sure it's safe, in terms of oxygen crash/dead algae, harming
beneficial bacteria, etc.

What do you all think about the bottom drain issue? Can I get by
without one if I vacuum or scoop the bottom with a net on a long
handle or both?

Joan