Well, there is going to be population flux to begin with, so that isn't going to be the biggest factor. They will reduce their numbers to a manageable load regardless. Plus, a handful of good, back-to-back water changes will dilute that artificially induced concentration when all is said and done. Beyond that, I don't think the OP was intending to raise concentrations that high anyway. I think the original intention was likely just 10ppm or so.