You most certainly can.
Just keep it under the substrate so it stays slow release.
You can fill gelatin capsules which are available on line or many health food stores, or freeze the Osmocote into ice cubes.
As for dry ferts, http://www.greenleafaquariums.com/aquarium-fertilizers-supplements/micro-macro-fertilizers.html
$19.99 for what seems to be about years worth for most folks.
Just keep it under the substrate so it stays slow release.
You can fill gelatin capsules which are available on line or many health food stores, or freeze the Osmocote into ice cubes.
As for dry ferts, http://www.greenleafaquariums.com/aquarium-fertilizers-supplements/micro-macro-fertilizers.html
$19.99 for what seems to be about years worth for most folks.