Worm Castings go at the top of the list because they make an excellent soil replacement that will also look nice for people who like to grow their house plants in arcylic or glass containers. Worm castings are lightweight and soft, providing a loose material that is high in nutrients and totally chemical free to help plants grow plenty of roots and maintain great moisture. Worm castings hold so much water that using them will also reduce the amount of watering that will need to be done to maintain your urban jungle. 

There's also no need to replace the soil in your existing plants because you can just top them off with a thick layer of worm castings to add nutrition without disturbing your plants' roots. The same can be done fo rplants growing in leca clay balls. The water you add to your plants will soak up the nutrients and deliver them to your plants' roots. 

Well...the fish can't really help it, can they? They have to let it go where they swim, but you can interrupt the natural cycle by taking out some of that good fish water and watering your house plants with it. Although fish water works wonders for most any house plant, it is a superior choice for urban jungle enthusiasts who keep some of their plants in leca as it prevents you from having to add any physical fertilizers that may detract from the clean look of the leca clay balls that many find so alluring. 

Although many people already keep pet fish, you can retrieve some old fish water from local fish shops, Pet Smart, or Petco for free as they are just going to throw it out anyway. Thereby you can save money while keeping things fresh and natural for your house plants. 

Got ducks? An unusual enough pet, ducks also exist on ponds available to the public, you just have to be willing to fish some of that water out and drag it home for your plant children. Of course, if you've already got a pond, adding some ducks isn't the worst idea I've ever heard, and you'll be able to go to your backyard whenever you need to fertilize your plants. 

Ducks, like fish, poop around the clock, so while they are in the pond... they are adding a high nitrogen fertilizer right into the water. Of course, the more ducks, the heavier the nutrient load of the pond water, so it's a good idea to either water your liquid duck fertilizer down so as not to overwhelm your house plants with too much of a good thing.