I have 4 extra colorimeters I could trade for some other probe(s). It's the old square box type. (But I do NOT need temp probes, pressure sensors, pH sensors, CO2 or O2 sensors, nor motion detectors, or light sensors, or conductivity probes - I've got plenty of all of those). Ideally I'd like to trade for a spectroVis Spectrophotometer or a Force Plate.
-SDowding in Wyoming