Holy crap, I had no idea that dosing and or adding magnesium to the tank would kill copepods? What would you consider a lethal dose? and would just adding a few ounces to counter balance a water change also kill them? When i used miracle mud in my fuge i had tons of life in there. Growing chaeto gave them room to live and i fed phyto. Since then , i got ride of M.Mud and went bare bottom with chaeto, but that didnt seem to work good. Now i have 3 inches of live sand and crushed coral and chaeto , but have no growth of anything live in the fuge. I spend 20 bucks a month adding copepods to my tank just to keep the mandarin happy. All this time i could have been adding them and turing around and killing them with Mag. There's just too much to learn...arrrrg. LOL