Osmocote® Flower & Vegetable Smart-Release® Plant Food
should be fine, in case you want to browse around the site, heres what you look for.
If you want trace aswell, go with the plus.
numbers like 14-14-14 thats the NPK, macro ferts.
Release, normally its 4 months for osmocote, but you can find longer
Just as any fert, its not is it safe? it's how much is safe. When laying out your substrate, you got choices in how you want to layer it. Some go straight with ADA, but since you are looking at macro ferts, im guessing you are going inert. So i'd recommend a layer of sand, then SPRINKLE osmocote on the surface, don't layer it, only need a sprinkling. then add your top 1-2inches of substrate.
If you are using it as root tabs, then do so, just think of the size of the standard root tab and place where needed. Keep in mind this stuff floats.
If you fertilize your water regularly, like EI, you wont see increased growth with osmocote, what you get is stability over the long term, the plants will draw from the substrate when needed, so it'll last much longer than the 4 months.
if you are looking for quick growth though, osmocote wont help, you need a plant food spikes (ie Jobes 13-4-5) they are dirt cheap, think like 60 of them for $3. Great for flowering plants