[Dailydrool] non toxic algaecide for fountain

[Cheryl Stafford]

I was wondering if anyone on the list would know of a non toxic product 
that I can add to my outdoor fountain that would kill the algae but not 
hurt the dogs.  I try to stop them from drinking the water; their 
outside bowl is right beside the fountain plus they pass right by a bowl 
on the porch, and they still drink out of the fountain!  The motor clogs 
from the algae and shuts down the fountain so we'd like to kill out the 
algae because cleaning is very difficult due to the fact the fountain is 
made from slate and is very heavy.
I thought I could try white vinegar since it seems to work for 
everything else but also decided to ask here as I know many of you are 
naturalist.
I appreciate any info.
Thanks,
Cheryl
Otter, Radar and Mollie the Bloodhound