I need help if possible, i have recently bought a milwaukee dissolved oxygen meter for testing compost tea (the 160$ one). i did all of the calibrating and everything properly, everything seemed to be working correctly last night, the reading was about 8 in my brewer with a bubbler going.

This morning, however, the reading has gone waaay down, close to 0 readings in the compost tea. I know that this is not possible, aerobic microbes will not consume ALL of the oxygen, once it hits about 4 ppm there will be a huge die off and they wont compete with the bubbler anymore so after that it should start to climb back up. it also smells quite earthy and nice(like its ready).

I tested the meter in normal chlorinated sink water and it reads about 5.7 so it seems about right. I checked the calibration, changed the membrane and the electrolyte solution. still exactly the same as before.

I have 2 theories, 1 that the microbes have solubalised the minerals in the solution and this has caused a salinity conflict and made the readings go whack. From what I read, the salinty should make the readings go way up, not down.

my second theory is that the microbes are consuming the oxygen at the tip of the probe so fast that there is no chance for the meter to tell me the correct oxygen reading, which would mean this is not the right type of meter to use for this, although I have never read anywhere online that this would be the case

If anyone knows of a forum explaining this problem please post a link because I cannot find one anywhere. thank you in advance for your help