No it's not a coincedence that a Bacteriacide would have helped cause the Algae Bloom.

Your Pond and specifically your Filtration System develops what's called Aerobic Bacteria, which helps process and clean your water. By using this chemical and NOT by-passing your filtration system, the chemical has killed off most (if not all) of this beneficial bacteria.

I just had the same thing happen when I treated my pond with Potassium Permanganate. I forgot to bypass my filtration system and within a couple of days I had Green Water. It will take 2-4 weeks for this bacteria to accumulate again in the filtration system. In the meantime, don't be surprised to see your ponds water turn Pea-Soup Green where you can't see anything.

However, this isn't really bad for the fish. In fact is has some benefits. The bad part is that you can't monitor your fish closely enough to determine if they're having any problems.

You can somewhat speed up the process of this re-generation of Aerobic bacteria by aerating your pond more and specifically your filters.

Some people advocate the use of UV lights to eliminate Algae and it does work. You will often read in these posts about them. However if you do use one, turn it off once the algae has been eliminated, because it also kills Aerobic Bacteria.

PS: Please do me a favor and edit your profile to include your location. A country or State will do. Thanks