I was using a 29g to help treat a grouper with ick, so I only filled the tank half way and I used a treatment with coper in it. A week passed and the grouper was good to go. So I sucked the water out with a gravel vacuum and rinsed the sponge filter out and filled it up with new water and I would like to put a lobster in it. Would their still maybe coper in the tank? I couldn't fully pull the tank out because it's in the stand of my 55 reef. I couldn't get any test strips for coper. Am I safe?