If someone is selling compost tea, especially if they claim to follow it with a microscope, they should be able to show you something similar to the following.
The following clips demonstrate the changes that an aerated compost tea (ACT) goes through over time. Please excuse my unusual form of narration. Note that the following brews were all made using simple ingredients as itemized on my webpage (good finished but fresh vermicompost at 2.38%, black strap molasses at 0.50%, fish hydrolysate at 0.063%, feed grade kelpmeal [not necessary!] at less than 0.25%, soft rock phosphate [not necessary!] at 0.063%) Lately I have been making ACT successfully using only vermicompost and molasses.
First at 18 hours, the early stages of a brew, normally we see the development/division of bacteria/archaea and the growth of fungal hyphae. If one is seeking a fungal brew for some reason, this is the time to use it.
http://microbeorganics.com/18hrs2vcfree.wmv
In the following clip I identify an amoeba as a naked type but in retrospect it may be an active testate amoeba.
http://microbeorganics.com/18hrs3vcfree.wmv
Usually some time between 24 and 40 hours flagellates and/or naked amoebae excyst (hatch out) and begin dividing every 2 to 4 hours so the population increases rapidly. Flagellates are the small globe-like creatures moving about. They are larger than bacteria/archaea but normally smaller than ciliates. It is the flagellates in ACT which are mainly responsible for cycling nutrients to your plants. As they eat bacteria/archaea they excrete ionic (available) form nutrients to the roots. Amoebae and ciliates also contribute to this but too many ciliates can be a sign that there may be an abundance of anaerobic bacteria and the brew is on its way (or has gone) downhill.
http://microbeorganics.com/36hrsvcfree.wmv
At 42 hours we still have a good brew and this is often the stage I usually apply it at but I recommend 36 hours to folks who do not use a microscope. You can see that ciliates have come to life by the presence of the beautiful vorticella.
http://microbeorganics.com/42hrsvcfree.wmv
Finally, at 60 hours takes a very efficient machine and good monitoring with microscope and O2 meter to ensure good quality. Although it is not stressed in the narration one can see the increasing presence of ciliates whizzing around out of focus. These are normally larger and faster than flagellates and can indicate the presence of too many anaerobic bacteria. Usually if the brew is continued on past this point it degrades rapidly, with ciliates and anaerobic bacteria dominating.
http://microbeorganics.com/60hrsvcfree.wmv
As long as there are much greater numbers of flagellates and/or naked (active) amoebae than ciliates there is no worry because ciliates also cycle nutrients. It is possible to run a perpetual brew but there will always be a down cycle where undesirable organisms dominate until the new [vermi]compost and foodstock kicks in (starts being consumed and the correct microbial groups begin multiplying again) and homeostasis is established. I have seen this down cycle persist for at least 24 hours.
Shops selling from a perpetual brew:
If one is selling tea to customers from a perpetual brew, how do you decide which customer(s) gets the inferior tea. There are people who did the testing of perpetual brews a number of years ago and assuming that ACT is about achieving a consortium of diverse nutrient cycling microorganisms, they concluded there is greater efficacy achieved by starting a new brew each time.
Those who advocate the perpetual brew support their method by alluding to some mysterious hidden diversity which one can not know about without DNA testing. This is complicating the use of ACT and [vermi]compost far beyond its simple form and use within the microbial nutrient loop. They are confusing bacteria and archaea which fix nitrogen (and other nutrients) with the nutrient cycling previously described, wherein nutrients are cycled by protozoa feasting on bacteria/archaea and excreting bioavailable nutrients taken up by roots. The diversity we are looking for are bacteria/archaea and flagellates (and amoebae) mainly. Fungal hyphae provides an ongoing food resource, binds soil aggregates, provides microbial pathways, degrades organic matter and increases moisture and O2 holding capacity. There is no mystery here, no specialty agents (although there could be) and it is as easy to see that diversity, with a microscope as it is looking for robins, sparrows and crows in your back yard with binoculars.
The folks who are perpetuating this mystery bunk to advocate perpetual brews, as far as I can tell, do so to line their pockets. They do not appear to back up their statements with data and criticize other brewer sellers who do. They entice hydro shop owners by illustrating how they can price gouge their customers. Amusingly they also state on their site that one should not brew beyond 24 hours because the microbes must be applied hungry
..Yikes!
(bookmarked)