When I picked up the Fadal, one of the big upgrades I was looking forward to was easy to use coolant. I had bad experiences with coolant on my PM940: coolant growing stuff, limited pumping power and coolant volume for flood coolant, and poor efficacy from MQL/mist coolant. The Fadal enclosure and coolant tank solved most of those problems.
Picking a coolant is a game that even most of the seasoned vets on Practical Machinist don’t seem to have a good recipe for. I went with Trim Microsol 690XT because quite a few members of PM reported getting long life and no issues with smell or rust.
I mixed in a 5-gallon bucket, and checked concentration with a refractometer, to confirm it was in the 10% range, the poured the bucket in the coolant tank (which was already cleaned — I also replaced the coolant hose). For some people concentration alone isn’t the best indicator, at least according to some of the applications engineers for these products. Hard water or pH imbalances causes issues, the details of which are over my head.
Now the real issue starts once you have the coolant mixed and in the machine. That problem is the way oil which is mixing into the coolant, and which allows the growth of anaerobic bacteria that make the coolant smell (and presumably reduce the lubrication qualities of the coolant). I bought a NexJen 1500 oil skimmer, which uses a pump and float in the tank, as well as a small separate tank to actually skim. I hooked this up to standard 120V household timer, and it runs for about 1.5 hours every day, based on the results I initially achieved running it for several hours.