Use equal parts of Grow Micro and Bloom. I would suggest using 5ml per gallon. (Each).
For 20 gallons of actual water (20 gallon res' might only habe 18 gallons +/-)
Use 100ml of each into 20 gallons. Check you PPM. You want to be around 1000 ppm PH 5.8. 800-1200 will be fine. Let me know what the ppm reading is afterward.
I run my flood and drain table once an hour for 10-15 minutes. You can set a recycle timer to allow for any time period in between. Most e and F growers like to run 15 on and 45 off. Watch you plants and check medium. In extreme heat you may nee to run pump more often. Bottom line is that you want Oxygen to be available to the root zone during pump off.
Hope this helps.