Actually you got that backwards. Your bio-filter doesn't introduce bacteria to your pond, the bacteria, that is omnipresent pretty much everywhere on our planet, colonizes in your bio-filter, and on every other surface in your pond.
Bottled "bacteria?" is product sold to the naive which is a bottle that is suppose to contain viable nitrifying bacteria to help colonize your bio-filter. Problem is it is sold in an air tight container, and generally sits on a self in a store somewhere until somebody buys it, and as most people are aware nitrifying bacteria needs a constant supply of oxygen to survive. On a warm day you could wipe out the bacteria colony in your bio-filter just by turning off the water circulation for a 24 hour period, how much less likely would it be for the bacteria to survive in a seal container sitting on a shelf for months at room temperature. Sure some bacteria could survive in a dormant state in that bottle, but we are literally living in a bacteria soup that is teaming with bacteria, living and dormant. Adding a bottle containing deeply dormant bacteria to your pond water would be like shaking a salt shaker on the beach in hopes of making the ocean saltier.
Of course the ponding hobby is not the only place this scam has gone on. They also sell supposed bacteria for your septic system, and compost, both of which are also useless products that are totally unnecessary, and yet there are companies out there that make millions on these products, and those that will argue to their graves that these products actually work.
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