If you were to crush up Osmocote Plus and toss it into the water you would end up with ugly, nasty looking, green water. Plus it would also promote algae growth like crazy.
I personally do the exact thing you're thinking of, I add 12 grains of Osmocote Plus into -00- size capsules, and just bury them into my substrate. All of my plants are doing great, and because of the Osmocote my 2 Tiger Lotus plants will not stop growing to the top of the water. I have to trim the Tiger Lotus' once a week because if I don't my other plants get absolutely no light.
Then I also use 1/4 teaspoon of Azomite to my 55 gallon tank once a month, and it helps with adding nutrients to the water column. I have a Anubias Nana that has 8"x4" leaves on it because of the Azomite. Azomite is also shrimp safe, it's used in aquaculture farming of shrimp and fish. It creates twice the growth, at twice the pace compared to normal growth standards.
Video of the effects of Azomite in aquaculture
Then below is the guaranteed analysis of Azomite
DO NOT WORRY
- the copper found in Azomite will NOT harm shrimp due to the age of Azomite which is around 30 million years old. You can find out more @ Azomite.com in the FAQ section. WARNING
to dosing with Azomite, remember I use 1/4 teaspoon per 55 gallons of water once a month, so you need to base your dosage on mine, and how much you should use per dose. Overdosing Azomite WILL
have harmful effects on your plants, as well as live stock.