well i am lucky because i can get sponge at wholesale.... but to answer your question, I would recommend talking to your lfs about getting live sponge for feeding. We have several customers that try to always keep live sponge in their tanks, so they let us know when they will need more and we order it for them. If they bought their angel(s) from us then we will sell it to them at our cost, but we dont take it out of the bag and aren't responsible for the quality (which it is just food anyway). We let them know when it will come in and they pick up the bag and pay. It can be costly, like normally $15 for a decent sized sponge that lasts me around 2-3 months (my angels are still only about 4"), but I like knowing that my fish are getting a good diet.