Many people have found WaterWetter to be unsuitable for our application. It seems that it coats surfaces with some agent affectionately
called "white goo" when it gets on your tubing. This is second hand information as I have never used it, being perfectly happy with Ethylene Glycol + distilled water + never mixing metals.
The pump used in your reserator is very low powered, consequently I would not recommend using an additive that raises the viscosity of your coolant very much at all. I would try the stuff that comes with the reserator. If it stinks too much when using it, ask again.
If it were me, I would lose the pump in the reserator, and put a DDC in-line (in case). Then use a more tried and true mixture of anti-corrosion agents.