Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
Bacteria bloom is grey or white, not green.
Green water algae is green, though it can look grey or yellow when it is just getting started.
In a case where you know there was a temporary increase in fertilizer (decomposing food) then a water change that removes the uneaten food might be all that is needed, perhaps one more a day later just to be sure.
It is OK to do large water changes if the GH, KH and temperature are matched. I test the TDS, too. Fish can handle changes in pH pretty well. It is drops in TDS that cause problems.