Thoughts
At the time of writing, InertX pricing is as follows.InertX PF5070 550g (310ml) Pro liquid coolant - £23.95
InertX PF5080 550g (310ml) Pro liquid coolant - £28.95
InertX PFX-90 1KG (560ml) Pro liquid coolant - £29.95
InertX PF5070 1KG (570ml) Pro liquid coolant - £39.95
InertX PF5080 1KG (560ml) Pro liquid coolant - £49.95
With the much cheaper PFX-90 doing the exact same basic job as the more expensive 5080/5070 PFCs, unless you're extreme cooling using InertX, there's little reason to buy any of the others, especially for the extra price.
Also, with 560ml costing at least £30, you won't want to refill your system that many times given that it likes to evaporate outside of a container, and you also might need more than one bottle per refill, depending on your system's capacity, making it more than a little expensive.
However for the peace of mind it gives you, in that your hardware won't die if it leaks and that there's no real chance of corrosion or algae build-up, it's worth at least considering.
Ultimately, save for seriously chilling a coolant to sub-zero temperatures using another refrigerant system or a cascade, there seems little point in buying InertX unless you're desperate for peace of mind about leak damage to your hardware. For me, properly leak testing your water-cooled system is enough to get that peace of mind for free. It's simply too expensive for too little InertX, to replace the £2, one litre bottle of de-ionised water from the supermarket.
£30+ buys you comfort, but little else. Saying that, I'll be endeavouring to test InertX in such a hardcore system in the future (in a super-cooled GPU and memory chiller loop), to see what it gets you in that scenario.
You can find InertX at InertX.com.
HEXUS HIGHLY RECOMMENDED
Pros
Doesn't conduct electricityLow freezing point for chilled coolant loops
Similar viscosity to water
Doesn't allow algae build-up
Very long shelf life
