I can't find any thing in my books about CF. A multimeter doesn't have an internal electrical source
to send across its electrodes to get a ppm reading. A multimeter uses an external electrical source to
If you leave the water flowing you should put an air pump
and air stone in your nutrient
supply your plant roots with oxygen. Some times just the movement of your water is enough to add
air but those air pumps are so cheap it wouldn't hurt to add one.
The ebb and flow
action of the bottle gardens suck in oxygen to the roots when the water lowers and
pushes the bad air out when the water rises.
Expanded clay aggregate lasts forever but I clean and wash it with a 10 % bleach solution between