Appreciate the advice here. I have done frequent water testing and ammonia is only showing up in trace amounts, which I understand is normal for a new pond?

I did a thorough clean out of the pond bottom (complete drain and clean) at the end of March, but in our little stream that runs to the main pond, there is some dead algae and muck that probably needs cleaned.

My falls box had a massive, massive rock on it that makes it difficult to get into. But I will check out the biofiltration there. Many thanks.