birds love waterfall -too much!

I have a small two tier waterfall(about 8-10' course) ending in a
small 90gal pond.

I had it made partly to attract birds to my property. Well it's
working alright. Maybe too well, Think every bird in my town is
coming for a dip. I don't have in it cause my two Labs would get out
their fishin' poles ;-}

Being a newbie, is there anything I should know before it's too late
about maintaining a clean and healthy water area even though it's
small and I don't have fish. No algae/moos problem yet.

TIA

All the best,

Larry
Southern Ontario