Removing Coralline off Overflow

I am trying to figure out a way to get the coralline off my overflow.The tank is running so chemicals are not going to work.
I cant scrape at it because it will cut into the plastic.
Any way to do this without ruining the overflow?
im kinda OCD about keeping the tank clean and this is the only thing i cant get the coralline off of. its driving me nuts!

 

I got turned on to a plastic mesh sleeve by my LFS that you put on the outside of scraping pad. I use it for my acrylic tanks and it works the best.

You can also use a tank scraper with a plastic blade.

If the overflow is curved at all you can use an old credit card.

 

Always wondered about this myself. I never tried this but just throwing it out here FWIW.

I thought about turning off return pump and filling overflow with really hot water and letting sit awhile. Then flush the overflow out with saltwater or removing the standpipe to empty the overflow then siphon then sump. It should kill the coralline making easier to scrape.

 

i havent tried the Credit Card yet. im just worried about it leaving a bunch of scratch marks in the plastic. maybe ill try on a small section first and see how it goes.
fyi this is a standard corner overflow on a RR tank.

 

when I trim my chaeto back I wad it up into a ball and use it like a dish scrubber on my glass works great cleaning glass and puts some pods in the tank best of all doesnt scratch works like a scrungie pad