I don't remember when the Easy Blade came to market, but it's a piece of plastic that you glue to a Magfloat magnet.  Affix a nice clean new razor blade (it's a specific one for this device), and you can work your way around the tank, carving off stubborn algae, coralline, and get into those corners that normal magnets can't quite reach. I like to use it near the sandbed too, so that area is crystal clear to see invertebrates doing their thing. And around the top rim, carving off whatever clings there.  It also takes off calcification on rimless tanks.

I probably paid $18 or $23 for the original part, and buy a 10-pack of blades from time to time. I also had to buy a Magfloat, because I only use the Easy Blade once every month or two. I didn't want it attached to my regular cleaning magnet.  When the tank starts to have that dingy look, that motivates me to install a clean blade and work my way across all the glass of the 400g and the 60g.  It's important to make sure the blade is in perfect condition, or you'll scratch the glass.  Each razor blade is double-edged. There are some words printed on one side of the metal face, so the first use I install the blade with the words oriented as if I were going to read them.  That's how I know that's the first edge, which after being used is now "old" and I won't use that edge again.  

Once done, I remove the blade carefully and rinse it clean in tap water. Next, I coat it in cooking oil and wrap it up in a paper towel and roll that up, and put a clip on it to keep it contained. This is how I know there's a razor blade in there and won't get accidentally cut.  Six weeks later, when I'm ready to use it, I'll find that clipped paper towel in the spot I usually leave it (bottom of the food basket under my tank), and install the blade with the printed words upside down because that is the other "new" edge.  I never leave the Easy Blade in the tank because the razor blade will rust. Leave it there too long, and you'll discover a rust line on the glass where it was resting. No bueno!

That's been my routine for years, and my method of cleaning and storing the blade makes using the Easy Blade pretty affordable long term.  You can find it online or at your LFS, usually.  I bet now that you've read this, you want to clean your tank extra well too. :)