I went to a local garden center and the Osmocoat is only $5.99 for 3 lbs.
I like the price.
If you can find a decent clean lake around your area, get some of the sediment from the just below the low water mark. Rinse in a bucket and allow to settle for a day or two, decant off the water and allow to dry into a good paste.
Mix the osmocoat with this paste.
Freeze for an hour, insert.
Some folks have used the osmocoat straight, then sprinkled it over the sediment, then pushed all the little balls into the sediment.
Blah.......too much hassle.
I have redone a section of the tank, uprooted things and move the sand over to one side, then dig down and add the layer on the bottom, then recover with the sand so the osmocoat is now on the very bottom.
After 3-4 weeks and doing this process each week for say 1/3, 1/4 sections, the tank is pretty much fully recharged. Less messy than soils, but the organic matter in soil helps. So a bit of trade off.
I use 5 grams of osmocoat per 4 gallons of tank.