I have no formula. What brought the idea about is that I keep this watering can to put used coffee grounds in -- usually 2 or 3 single serving Eco or Kcup or single serving French Press (about 4Tbs ground coffee) at a time. I also swish out the last dregs from my mug and that last bit of juice, coconut water, etc. from cartons when I rinse them out for recycling. Leftover bottled water, rice washing water, etc. I used to use this straight to water my indoor plants with.
Well, it occurred to me that it would be much better to keep the stuff aerated than to allow the contents to get stagnant. As long as I was brewing it, intentionally add more good microbes to eat the food and populate: So add to that up to 1/4C vermicompost, a glug of Activated EM or dollop of molasses.
I use the smallest air pump I have. it came with a cute gumball machine aquarium I had years go. (I think it's like 300 or 500). I tried using the 2000 while I was looking for this little one and the bubbles nearly overflowed before the air stone hit bottom.
Anyway, now it's way concentrated so I dilute into 5 gal bucket of water and that makes enough to water all of the container plants I brought inside. I need to water them all at least once a week, some of them twice a week.