Again, since I make my own root tabs it makes things a lot easier to manage, and saves me a lot of money by making my own. I use size -00- capsules, and fill them with Osmocote Plus, currently I have around 25 pre-made root tabs sitting in my stand. I add new tabs to my 55 gallon tank every 4 months like clock work, and because I got the 4.5lb Osmocote Plus 9 month ago, I still have pretty much a full 4.5lbs left.
You figure the 4.5lb Osmocote Plus cost around $20 + $9 for the 1,000 size -00- capsules = $29; Leaves me with a major supply for over years to come. Which saves me a lot of money in the long run, compared to using say API or Flourish root tabs which won't last as long as the Osmocote Plus does because of the time release formula that Osmo. + contains.
But that's just what's in the substrate, but I also dose the water column using a dry fert mix with water.