Good spot Clive, it surely was PO4... I've been following this for weeks thinking "this is so strange, Garuf has the WORST luck - he always has algae problems!". But there was, of course, a logical explanation...ceg4048 said:There must be something wrong with your dosing or flow. GSA doesn't just show up widescale unless there is a PO4 shortage. Neither does BBA. Could your powders be mixed up or could you have massively miscalculated? This is very strange.