I am actually just getting into water cooling so I have no experience with algae, just sounds like a miserable experience getting it and want to try and prevent it.
Here is a link on some tubing that might be cool. Kind of neat blue color and almost looks transparent but the salesman said it wasnt. Hes sending me a sample piece to check out.
http://www.eldonjames.com/html/FlexeleneSilver.html
Also did a little research on silver additives and found some interesting stuff.
Maybe a dose of this stuff might help prevent or get rid of some existing algae or whatever growth conditions?
http://silver-colloids.com/Pubs/AboutIonic.html
http://silver-colloids.com/Reports/ionic-products.html
http://healthequip-store.stores.yahoo.net/cosiso.html