Here is a helpful hint for your moisture/Ph meter, the three in one kind that tests moisture, Ph and light with the two probes that you stick into the dirt. I am using it in my worm bin because it's the first time I am using coconut coir (fiber) and it holds a lot of water.
I found the meter that I have had for a couple of years wasn't reading very well. I put it in a cup of water and the needle stayed just at dry/moist. The probes were dirty and corroded so I washed and scrubbed them then put them in a cup of water again, still the same reading. So I got out some white vinegar and switched to the Ph mode and the needle stayed at 7, vinegar is acidic. So I wiped the probes off with a paper towel and a lot of black grime came off. I think one of the probes is made out of aluminum and it had a oxide layer built up on it. When I put the meter back in the cup of vinegar it went to around 5.5-6, progress. I put the meter back in the moisture mode and into the water and it spiked to the far right/wet side. So it looks like cleaning it every once in a while with vinegar will keep it working.