I see all the time people are putting Oscomote Plus in their substrate as a sort of slow release root tab.. I looked a few places and I couldn't find Oscomote Plus, only the regular kind, and I know the 'Plus' variety because it does include both some micros and macros. I know Oscomote Plus is supposed to be safe, except possibly deadly to shrimp but I just have one amano shrimp, and although I don't want him to die, I am willing to sacrifice the one for healthy sword plants.
Here's a PDF I found with Oscomote Plus's analysis: http://www.alliedbotanical.com/pdf/Osmocote15912.pdf
It is on the second page.. I'd copy and paste if I could.
And then here's Ironite Plus for comparison:
Total Nitrogen 12% (Ammoniacal Nitrogen)
Available Phosphate 10%
Soluble Potash 10%
Total Iron 2%
Total Manganese .10% (Water soluble Man .03%)
Total Zinc .10% (water soluble Zn .02%)
It says derived from Ammonium Sulfate, Ammonium Phosphate, Muriate of Potash, Sodium Nitrate, Iron Sucrate, Iron Oxide, Manganese Sulfate, Manganese Oxide, Sodium Molybdate, Zinc Sulfate, Zinc Oxide
Was planning on popping some in some ice cube trays, freezing them with tank water, and sticking them in the substrate below my swords I've got coming in the mail.