Fresh water comes out blueish!!

Got a new case (Aopen H700B), which ment it was time to redo my H20 setup. After I was done leaktesting, I drained out the fresh filtered water and noticed it was blueish. I have never used any dyes in my system. Only used WaterWetter. Radiator is the Heater Core and a block is a Dangerden Maze1 powered by an Enhiem 1250.

Is that just growth in my radiator thats coming out? If so, that mean I should be using more waterwetter?

I've had the same blueish water after draining my water cooler. I too used water wetter at the time.

I have no clue where its from, but I wouldn't add more water wetter because of it.

Its poison!!! j/k but you never know....

Well you could add some bacteriostat (from sears) if its bacteria. I've had green water but not blue. Perhaps someone else can enlighten us.