How to clean Maze3

I recently disassembled my watercooling setup in order to make some changes. After removing the waterblock, a maze3, and emptying everything the block sat on a table. After a few days this white/greenish powdery stuff 'grew' in the block. The same thing grew in the old tubing, but not in the GPU block. The block was completely clean when everything was connected, and the system was run with distilled water, and the radiator is copper as well.

So, basically how do I get this out of the waterblock? I would really like it clean before I hook everything back up.

open up the block with an allen key, and you can try using some alchohol an a QTip and see if that works, and if you get it somewhat clean, try some vinegar or ketchup (not joking)

were you only using distilled?

Elusion used Tarn-X to clean his block. He did an awsome job at it too. You should try it

Looks like corroded copper to me, try running your setup with like 15% antifreeze next time.

For getting it off, just open it up and wipe it off.

if u're too lazy to open it up or don't have the allen key (mine are abused, they look like circles now) you could run some salty vinager throught the block for a while (that would be a combination of salt and vinager ) works for me..
gotta love that penny cleaning highschool chemistry project.. wow i learned something from high school, i'll be damned