"Nedra" sez:
Yes it is worth it! ... the instructions follow:

1 Tablespoon for every 1,000 gallons of water. Swish in
a glass of pond water until dissolved then pour it around
the perimeter of your pond.

Two weeks later....
I use the same as above... I think the instructions say to
only use 1 1/2 tsp per 1,000 gallons.

You can see why it lasts so long ....
also, do you really think we would all use if it weren't
"worth" it??

Well, yeah. Magnetic bracelets, Madame Cleo, cell phone "radiation
shields", cellulite-reducing creams... people use and swear by lots of
things that not only obviously don't work, but have scientific and
statistical evidence of not working.