BoyPete wrote:
Is there an easy test for oxygen content in pond water?
I have an air pump with twin outlets combined into one, feeding an
airstone in the pond. Is there any advantage in putting a stone in my
box filter?

Supplemental question........... any reccomendations for airstones (in UK)
please. I live in a hard water area, and they clog in a few weeks.
--
ßôyþëtë
London, UK