CB1 :

Often when we have a reduction in our green plankton bloom { usualy due to rain or fert. diminishing} it is followed by visa. increasing and then brown plankton bloom with reduced visa. There have been several posts in the last week with the same problem . Ours is usualy self correcting and turns back to green in a week +- with sun and light fert. addition. See the posts below. Greg called it a red euglena bloom . ewest

http://www.pondboss.com/ubb/ultimatebb.php?ubb=get_topic;f=9;t=000110

http://www.pondboss.com/ubb/ultimatebb.php?ubb=get_topic;f=16;t=000069