GTX instructions clearly said to use HydrX as fluid to retain warranty so they obviously knew it would be hard to run with just distilled water. Glad you found out before it leak. I'm also happy to see a serious post about this after reading others (like the one using tap water or another which didn't specify what fluid clearly).

This should be kept for posterity to show why running with aluminium parts is a big no-no no matter how sweet manufacturers coat them to prevent them. What they didn't understand is that no matter how great the coating is made, all it take is just a pinhole (often around the barbs area since screwing a barb is bound to scratch the protective coat) to start the corrosion process.