it's like a $5 bag from home depot. i think i might just scoop it out continually, tho.where did you get the soil from. was it outsidr un a garden where ut could have had prior contami.ation w a algae or moss. usuy green alga is a type of cyanobacteria I believe so its totly possible. id go buy a 1 gallon pot n a bag of happy frog n replant it. or some pro mix.