Bubble Counter Fluid and Diffuser Contamination

[tackful]

Numerous diffuser manufacturers warn against using anything other than water in a bubble counter in order to avoid diffuser "contamination". Not sure what they mean by this. Blockage? Bacteria? Anyone know?
Frank

 

[dougall]

In case the liquid ends up in your aquarium... The bubbles can force the fluid up into the tubing and then into aquarium water,

 

[tackful]

I've decided to try Prime in the bubble counter. Perhaps it won't evaporate as quickly as water.