They're not that bad to keep clean. I service three tanks with artificial coral inserts.
If it's a fowler. You can dose small amounts of hydrogen peroxide to keep them looking cleaner for longer.
Then while you're doing maintenance, you use a scrub brush and give them a scrubbing before your wc.
Then once they get to the point of being really dirty. Pull them out, and spray them with bleach in your laundry tub. Let them soak in bleach for about 15mins. Rinse them in HOT water about 3-4 times. Then soak them in a bath of hot water with lots of water conditioner (about 5-10X more than you'd normally use). Soak them for about 15mins. Rinse again and they're ready to go back into the tank.
Done and done
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