Alage growth killer for 1/2 55 gallon white dog water buckets?

If what you have is a slimey stinky growth you have blue-green algae. Not really an algae, it's a type of bacteria called cyanobacteria. If its tough and green and adheres to the plastic very well you have normal algae. There is nothing harmful with regular algae. It just looks bad. If anything, regular green algae is filtering the bad crap out of the water. Green algae is used in sewage treatment all over the world. Not worth the trouble or expense trying to get rid of it. Blue green algae on the other hand can put off a toxic compound when it's running rampant, but that is rare. The only way to kill off blue-green algae is with an antibiotic and thats probably not worth the expense. All algaes grow as a result of too much nutrients in the water or too much light. Putting water containers in the shade and draining out dirty water keeps it down.