If you buy many worms regularly, won’t the people who breed them produce more? In my view that is not a problem at all; it helps those people earn a living. Buying these worms is not only to give them long lives and protect them from the fisherman and becoming bait for fish. There is no problem if they raise more. They’re not just growing from the earth as they probably think in the West. There are numberless sentient beings in the intermediate stage who have karma to be born as a worm. When the conditions are there, they are reborn; those numberless beings that have no karma to be born as any other being, only karma to be reborn as a worm. As that karma ripens, the conditions can happen. The conditions happen when the karma is strong, powerful.
So here we are not just rescuing them from the fishermen putting them on a hook and using them to attract the fish, not just for them to have a long life. Here we purify their negative karma and defilements and cause them to collect merit, to achieve immediate higher rebirth and liberation from samsara and enlightenment. Every single circumambulation becomes cause for their good rebirth in the next life, for them to meet the Dharma, to actualize the path and achieve liberation and, sooner or later, to achieve full enlightenment.
This is the incredible special benefit they receive. Therefore, even if people raise more worms, there is no problem. Sentient beings are born as worms not because people make them in a field, but because there is karma for them to be born as worms. So here, what we are doing is purifying their negative karma. We purify so many sentient beings of the karma to be born as worms, to reincarnate in the lower realms and reincarnate in samsara and experience suffering on and on without end, dying and being reborn, dying and being reborn, and experiencing all the sufferings in between. We are trying to help them end their suffering. Otherwise, these sentient beings would be born as worms numberless times, as well as hell beings, hungry ghosts, etc., experiencing those sufferings over and over again.*
*Liberating Animals and Other Ways to Benefit Them, Lama Zopa Rinpoche, FPMT, Inc., 2005, pp. 42-43.