Suddenly, something is destroying, one-by-one, my long Echinodorus
leaves. They're being reduced to skeletal leaves at night.

I have Ancistrus, Otocinclus and Upside Down Catfish. Which do you think
is the guilty party?

Is it a coincidence that my tank PO4 level is now a lowish 0.1 ppm? Are
they starved of algae and resorting to eating leaves? If BBA is still
hanging around I can presume that the stuff they thrive on is still present.

Nikki