Is there anyway to keep algae from growing in my nurse tank? The tank has a side bung hole so it doesn't totally drain out without me unstrapping it from the bed of the truck. I don't use it all the time but I do like to leave it in the truck when not in use. Problem comes when that little bit of water starts growing algae. So, is there anything I can do or put in the tank that will stop this or is the only way to totally dry it out everytime?