Has anyone done the Diy root tabs?
Any success?
Number one complaint would be the slow release fertilizer balls can make their way to the surface over time of the substrate, needing to be removed at some point. Otherwise they're easy to make yourself.
Higher concentrated fertilizers I place further away from main root structures, spacing them every 3-6 square inch, especially near heavy root feeders like echinodorus, Cryptocornes, nymphaea etc.
Shrimp safety is another question, as the trace copper in many garden fertilizers could harm invertebrates. So you'd have to experiment, although I use them in tanks with neocaridina, amano shrimp, nerite and other snails. Some fish may also be sensitive.
I've used miracle grow shake and feed, a shrub fertilizer from home hardware, and Osmocote plus (I don't have npk values atm).