hello everyone, i had bought a boxfish a few weeks back and he ended up getting to stressed and dieing in the tank. I took him out right away and flushed him but then i noticed that all my fish were breathing really fast and swimming really slow so i moved them to my other tank. I left my blue legged crabs and starfish in with a few other crabs and snails and things and they ALL died the next day. I emptied the water out and cleaned the rocks and did a nice clean up and then put new water in and got the levels normal. Then i went and bought a fish and it died soon after i put it in the tank. Then i bought another and it did the same thing!! now i dont know what to do. how to i get the poison out of the tank?