I'll weigh in on it. If you want to know what you have in the tea, you have to look at every batch for about the first 100 batches. After that, if your process is settled down, you can probably make a good, educated, guess as to the quality of your tea. But without the microscope, you can't know what you have. You just can't.
Having said that, if the tea started out with excellent smelling compost, and you used fresh water from a bacteria free source, and the tea itself smells good, it probably does not have any bad stuff in it. The bad stuff will not magically appear without being "seeded" into the compost. Using manure or anything stinky instead of excellent compost will definitely be a problem, though.
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