We use bacteria products. Here's what I have learned. First, every company claims to have "proprietary" formulations of bacteria cultures. They guard those recipes at all costs. That's because we can probably buy all the ingredients at most grocery or drug stores. I haven't yet figured out the price differences, because no one will own up to ingredients. So, there's no way to compare apples to apples.
But, we have gotten good results for the proper applications. Lagoons, retention ponds, ponds for aesthetic purposes..bacteria works well, as long as there is plenty of food for the microscopic critters. Dead algae, organic matter in pond bottom mud, will feed bacteria.
We have found bacteria to be an excellent alternative to algaecides in select situations. Algae has a rapid lifecycle, dying, growing, dying, using available nitrogen and phosphorus. Bacteria seems to tie up the nutrients and break the life cycle of algae, without the disruptive effects of some algaecides. But, expect to spend quite a bit more for bacteria than for algaecides.
Regarding pond muck, bacteria cannot possibly rid your pond bottom of all that black, stinky, gooey stuff. But, bacteria can certainly "eat" much of the organic matter, leaving behind a composted, digested layer of soils and broken down basic nutrients.
I haven't used any of the products in ponds where we are focused on raising fish. There, we add nutrients, manage fish, manipulate vegetation. Bacteria, for us, so far, has had minimal roles in managing recreational fish ponds.
