http://www.toybuilderlabs.com/products/3-00mm-glow-in-the-dark-pla-plastic-filament
Please note: Like most high-performance glow in the dark products, the Strontium-Aluminate glow pigment contained in this filament is abrasive. Using this filament will wear down your nozzle and other extruder components.
http://www.formfutura.com/175mm-easyfil-abs-glow-in-the-dark-green.html
abrasiveness Please be aware that Glow in the Dark filaments contain a relatively high concentration of extremely hard phosphorous particles, which have an abrasive nature. In general these phosphorous particles will accelerate the nozzle-wear of brass nozzles, much faster than unfilled filaments. We recommend to use nozzles from stainless steel or other hardened alloys.
So, there are 2 brands of nozzles that are hard coated upgrades for the MK8 extruder you have.
https://store.micro-swiss.com/products/mk8
https://www.p3-d.com/collections/duraplat-3d-extruder-nozzles
I have used both for years now.