Fish emulsion(crap) is a good source of N, just stay away from it for the last few weeks unless you want to taste it in the final product! I'm sure you know someone that has a tank, ask if they can try to strain the water next time they clean and give you the crap and uneaten food on the bottom. Generally things you add to the soil like fruit and bonemeal have to be mixed into the soil first and they give off the nutes as the bacteria breaks them down. Try doing a quick search for organic tea recipes, there's gotta be some good ones here...