I use Pottasium Permanganate (PP) to sterilise anything new i use for the pond, so i would have thought it would do the job for your trough. As theres no fish in it measurements dont really matter, give it a good dose and add an air stone to keep it circulating, if you leave it over night by morning it should have killed any nasties or release agents put on it. If its gone pale brown by morning it means its stopped working, and you could possibly dose again to be sure everythings been sterilised but i wouldnt have thought it will need it. hope this helps
Posted on Oct 28, 2005, 4:45 PM from IP address 82.38.197.142