http://www.vwrsp.com/catalog/product...ect_id=0007626
http://www.vwrsp.com/catalog/product...ect_id=0007628
I use these in cleaning glass and plasticware of organic deposites here in the lab. Both rinse easily and I have seen no staining of Nalgene brand plastics (only ones I use) or metal corrosion (however, most of my equipment is stainless steel).
http://www.vwrsp.com/catalog/product...ect_id=0022522
Specifically, Extran AP 41.
While I have not tried this product, it has been reccomended to me for cleaning tough organic growth.
Frankly, for home use, water and a scrub brush is probably your best option. Isopropyl alchohol (most any alchohol, really) can be used to kill algea (edit: actually, I suspect you are seeing cyanobacteria), however it precipitates proteins and DNA/RNA, leaving you wielding that scrub brush anyway.
long brushes:
http://www.vwrsp.com/catalog/product...ect_id=0006982