Carefull work with a soldering iron or find some plastic,the same ,Poly prop ,,colour doesnt matter or remove some exess plastic if any from around the edge of the tank and cut some slithers to melt in with a hot air gun or soldering iron, try to roll into or blend with the other plastic , i use a teflon roller but you could use a snall wooden wallpaper roller or similar
NED ,,Neds plastic repairs NZ ,mustangned at gmail.com, January 2011