Yes, Brandt Indicate 5 can be used in a tank mix with Captain and Imidan. Please review the Product Sheet for more information.
There is no exact mix rate of the label for Brandt Indicate 5. This is because the pH of your water is what determines how product is used. Per the product label: "Fill tank 2/3 full of water. Add desired amount of INDICATE 5 or until solution turns pink for a pH between 4.5 - 5.5. Fill tank with balance of fertilizer or water Add other chemicals. Agitate adequately to mix. If the tank solution turns clear upon the addition of the remaining chemicals and remaining water, add additional Brandt Indicate 5 until tank mix solution turns pink."