[MikeM]

There are spots under the pipes leading in and out of my vortex that gather mulm. I was thinking that the polyurethane foam used to bind together rocks around ponds might work to fill the gaps so there would be no place for settlement to gather. However, the directions do not say whether the stuff can be submerged, do not say if it has to be fully cured before being submerged, whether it has to be fully cured to be fish-safe .... in fact, it does not say much at all, except to wear old gloves & clothes when applying it!

Anyone have experience with Polyurethane foam in a submerged location??