These are excerpts from Tims' (MicrobeMan) website. He is the most knowledgeable chap I've come across when it comes to ACT's and nutrient teas. I follow his advice to the "T" (pun intended).
"In case I have not been clear enough above, our goal in making ACT is to extract, multiply and grow mostly aerobic microorganisms in as large a diversity as possible and inclusive of three basic groups; bacteria/archaea, protozoa [flagellates & naked amoebae] and fungi. (Some [vermi]compost will contain rotifers which are extracted into ACT. These cycle nutrients in similar fashion to protozoa and are a bonus if present.)
Making ACT is not about putting in ingredients which directly benefit the plants. The foodstocks used are strictly to feed or benefit the microorganisms which in turn benefit the plants.
When I jumped on the compost tea bandwagon years back I utilized the whole gambit of ingredients recommended by the current (at that time) supposed authorities. These ingredients or foodstocks included, humic acid, kelp meal, black strap molasses, baby oatmeal (oat flour), fish hydrolysate, alfalfa meal, etc. We used variations of these ingredients in our 1200 gallon ACT maker on our farm and microscopic observation showed success.
I also experimented with using some rock/clay powders as ingredients and observed differences in the microbial make up which had positive results applied to the soil and plants. The types used were mostly soft rock phosphate and pyrophyllite.
Along the line somewhere we left humic acid out of a brew and noticed an increase in microbial numbers so we stopped using it ourselves but, possibly irresponsibly, I continued to recommend it because the ‘bigwigs’ did so. It was not until I devised a method to test each foodstock independently that I began to change my tune and begin to go against the grain of the contemporary experts."
"By testing some ingredients independently in a liquid I observed;
1/ that humic acid in varying dilutions does not feed any sort of microscopically visible microbe. I observed that it actually suppresses microbial division and growth. This was confirmed by joint testing with Keep It Simple Inc. (KIS) in the Seattle area. We tested two of the most effective and popular brands. I cannot say definitively that all brands of humic acid will have similar suppressive effects in a liquid (ACT) but it is enough for me to discontinue using it or recommending it as an ACT foodstock. Please note that this does not mean that it is not good to use on/in soil….just not ACT.
2/ that kelp meal initially delays all microbial development in a liquid but does feed fungi and bacteria/archaea following 24 hours. If too much is used the effects are suppressive. From this I garnered that it should be used very sparingly and one must be prepared to brew a little longer if using this foodstock. Again, this does not mean that kelp meal is not a good thing to use in/on soil. It definitely is!
3/ black strap molasses (BSM) feeds both bacteria/archaea and fungi equally well contrary to what the A(A)CT aficionados were saying. The story was that BSM feeds only bacteria. This led to all sorts of misconceptions, even including ones made by USDA and Canada Agriculture scientists who declared that using molasses in ACT could lead to e-coli contamination. It is utter nonsense. Besides the testing I have done and ratifying assays carried out by KIS, it is common knowledge amongst many mycologists like Paul Stamets that BSM grows out fungal hyphae just fine.
4/ fish hydrolysate feeds both fungi and bacteria/archaea again contrary to the story at the time that it is mainly a fungal food. (I’m glad to see that story has now changed)
5/ alfalfa meal is also a decent all round foodstock which sometimes introduces protozoa cysts to the ACT. KIS has done more testing on this than I have.
The result of all this is that my attitude towards recipes for ACT has really evolved over the years with a trend towards the more simple. I know that there are a lot of people who place importance on creating a bacterial or fungal dominant ACT. At one time I myself was so influenced, however, the more I’ve learned and unlearned about living soil and a functioning microbial population interacting with plants, the more I’ve been led to allow the soil and plants to decide which microbes are actively needed by the rhizosphere team. What this means is that 9 times out of 10 I’m trying to create a balanced ACT with a decent ratio of the three basic microbial groups. When this hits the soil, some will go dormant to wake up later and some will be immediately put into action at the direction of the needs of the soil and plants.
The exceptions to this may be if I am attempting to battle a particular pathogen and want to attack it with a heavy fungal or bacterial (or a combo) ACT. In these situations some tweaking of recipes and timing can be helpful. If attempting these variations, a microscope is really the only way to confirm the desired microbial population. I have outlined some recipes which may trend towards a certain microbial group (or combo) or may assist with certain pathogens."
The bottom line: The proper ratios of vermicompost/compost and unsulphered blackstrap molasses will achieve a great ACT. If you want to add anything beyond that, don't overdo it. Some inputs can suppress microbial multiplication. You can always add these other ingredients you wish to use to a nutrient tea.