I had a lot of plastic plants in my 75 gallon community tank, but I've noticed for some time the fish that inhabit it (4 rainbow fish, 12 congo tetras, 6 pictus catfish, 2 kribensis) don't use them to hide behind or anything and pretty much they just seem to take up swimming space. I've also noticed when I clean the tank and pull up the faux plants I get lots of detritus stuck down in them. This last week I pulled all the faux plants out and there was so much crap released it freaked me out and after a thorough vacuuming and large water change I didn't put the faux plants back in. I actually like the tank better with just the couple of caves for the catfish and the fish seem to like the increased swimming room. Also once I'd removed the plants I found some of them had exposed metal in some spots where the plastic cover had worn away and it was rusting. Good grief why would there be metal in an aquarium decoration?