There are tons of ways to make homemade plant food rather than buying products of the shelves of stores. Save yourself some money by picking items off your own shelf.  From Creative Homemaking,

• According to another reader, Knox unflavored gelatin is really good for houseplants. They agreed that mixing finely crushed rinsed eggshells into your potting soil would give your houseplants a good boost. The eggshells are a good substitute for bonemeal.
• If you have a fish tank, when you change the water in the tank, use the water you take out to water your plants. Your plants will love fish fertilizer!
• One reader once a month pours a can of room temperature beer into each of her plants. She has had one plant for over 15 years.

I really like the fish idea, especially since we have a Beta fish here at home. Adding this to my to-do list!