There are those that would argue, the beneficial bacteria is already there in your pond and adding more, won't make much difference. Unless you add some aeration system to help it thrive. Then since aeration is the key, do you really need to add anything else? I agree, to a point.

If you don't have good aeration, save your money on additives until you get at least that.

In my opinion, the two together, work quite well. Not really sold on the blocks here, I like more of an even distribution, at the bottom, in the way that pellets offer. I was able to dissolve more than a foot of that stinky black sludge with the combination of the two, in just two years. It's possible aeration alone would have done it, I'm just not sure it would have been that fast.