Resin Coated Gravel and UG Filters

[sanford]

The LFS in my area stocks Estes brand gravel  that advertises an environment friendly resin coating on the gravel.  I'm not sure what advantage resin provides, but I am even  more curious about whether the resin coat reduces gravel porosity to a point where the gravel is less effective as bio-media for an under gravel filter.  Anyone have any experience with this?

[Levi_Aquatics]

I have not used it for those applications, but i have noticed that the resin and black color wears off the gravel rather quickly.

[gardenman]

Yeah, the durability of the resin coating isn't great, especially if you have plecos, goldfish, or gravel shifting fish. As to its effect on the gravel's ability as a bacteria refuge, it should be minimal. Most aerobic bacteria will populate the surface of gravel. They won't care if it's a natural coating or a synthetic one. The coating will increase the size of the gravel marginally which will slightly affect the amount of surface area available. If you have an inch of gravel in the tank and a fine grain or a coarser grain. the finer grain will have more overall surface area. The coating makes the gravel a bit larger, so you lose a bit of surface area, but it's minimal.

[sanford]

Thanks all. The gravel at the LFS is natural coloured with what appears to be a clear resin (Estes is the brand).  In this case resin breakdown should not discolour the gravel and it seems that its viability as UGF media is not compromised. Huzzah!