Wrench for a water purifier (Reverse Osmosis filter) resin tank cap

If you have a fish tank, and especially a salt water recifal fish tank, may be you have a reverse osmosis filter to purify the tap water you use for your tank.

Now I don't know about you, but the device I got came with a wrench to unscrew the fiber filter tanks, but none to open the resin tank (the last tank in the water circuit).

And it can be really difficult to open !

That's why I designed this wrench, and I'm now able to replace the resin without ripping the skin of my hand appart !