<https://forum.aquariumcoop.com/topic/12409-why-are-ugfs-not-very-popular/#comment-97528>
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"What other substrates have you used that did not perform well?\n \n\n\n\t Certainly anything so small it goes through would not work.  Like sand is difficult. I have used sand with a mesh to keep it where it belongs.  I was never happy with sand.\n \n\n\n\tTiny gravel/pebbles was okay, but if you keep a dirty tank, like me, then 1/16\" - 1/8\" inch sized pebbles as substrate is what I like.  \n\tGives the roots and worms room to do their thing. Oh yeah and the MTS!  \n\tYou might like this article https://www.sciencedirect.com/science/article/pii/S0075951111000399\n \n\n\n\tRemember when reading this, that they were not studing a UGF, so grain size is not as relevant to this study when using a UGF.\n \n\n\n\tFrom what I understood and used to draw my conclusion is that a UGF would increase the roots access to the nutrients.\n \n\n\n"
<https://forum.aquariumcoop.com/topic/12409-why-are-ugfs-not-very-popular/>