You already probably heard me mention my shrimp dieing. I suspect the copper from CSM+B since I dosed it according to Fe. I never saw any negative affects on my plants or fish though. But If I didn't want to keep shrimp I wouldn't care about the copper and keep on dosing CSM+B as always.
If you feel the need to be safe, use an iron chelate for iron instead and CSM+B just for traces.