<https://forum.aquariumcoop.com/topic/12409-why-are-ugfs-not-very-popular/#comment-97450>
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"I've been using the same UGF for 30+ years in my 29.  Yes, there is a lot of \"gunk\" under there, but now there are also plant roots feeding off of the gunk. My Nerites would vacation underneath until I added a piece of mesh to the lift tube.  If I get curious about what is underneath, I either do a water change through the lift tube, or thread a small dia. tube under the plate and syphon some material out.\n \n\n\n\tI have the Lee's product in the link.  I think I paid about $36. but that was almost 10 years ago.  Blame it on Covid.   After the last big aquarium move I got lazy and cleaned underneath only one of the plates.  When the powerheads came back online, everything in the aquarium disappeared in a thick brown cloud. In 3 hours the aquarium was mostly clear, and by end of day the water was completely clear.   The non-UGF aquarium took 2 days to return to normal.\n \n\n\n\tI like the UGF because: it works, it is inexpensive, I don't have to look at it, it will last almost forever, and except for adding a powerhead there is nothing else to buy.  The only downside is that for best performance, you are limited to a gravel substrate.\n "
<https://forum.aquariumcoop.com/topic/12409-why-are-ugfs-not-very-popular/>