I don't do the adding water from the tank into the bag thing, never have and have never had a problem. You can take any plastic bag (never used for anything before--like the plastic bags you can get from the supermarket produce section, or a baggie or sandwish bag, etc.) and dump the water and fish from your bowl into the bag and float the bag so the water temp gets to the tank temp. After about 30 mins (there's usually not a lot of water in the bag so it warms up fast), suspend a net over a container and pour the water from the bag into the net letting the fish get caught in the net. Then quickly put the net into the tank and let the fish go. Dump the water from the bag (now in the container) down the drain. Usually the water from the store is not all that different from the water you use so there's not a huge discrepancy that the fish need to adjust to as far as water chemistry/minerals, etc. are concerned.