You should be sure the water you use for top off and changes is free of both silicates and PO4
. Brown algaes will moreso be the result of silicates than anything else. As far as the mysis goes, you should try thawing it in some RO
water and then strain the shrimp discarding the water. That will help in adding additional PO4
. The tang should not really be eating meats as a regular daily diet. You should try getting some nori or other herbavor food high in spurlina that can be left in as a grazing food. Over time the tang will develope health problems if only fed meats. That will aslo help in cutting the feedings down.
Fighting conch's are the best for diatoms but a mixture of snails for the "over all" care of the tank are also necessary. Cerith, nassarius, trochus and nerite are a few good ones. If the water source is free of the silicates and phosphates, your algae problem will burn itself out soon. As long as those elements are being introduced, the problem will not go away.