i had this and was a nightmare to battle. tried raising the ph with kalk, increasing flow with more powerheads, lights out and massive water changes. what i did was researched and found what worked for me was
dont do water changes. the dinos feed off the nutrients in the water. use a turkey baster and suck up as much as you can. dont blow it around cuz it will just move to another location. have small refugium with a light with really, really slow flow and the dino will start to accumulate there. run a phosphate reactor. dont dose any carbon source or amino acids as this will fuel the dinos more. now this method is not gonna cure it overnight but took me another month to finally beat it. good luck