I use only very old aged water for the water changes. (I constantly keep a lot of aged water). The worms in my experiment were never washed with tap water. And also, I said I don't see any dead worms during the water changes. Normally, when I previously wash/rinse worms, I see a lot of dead worms in the mix.
I previously use a satay stick to feed the fish with Tubifex. But If I use the stick, I need to swirl the worms violently with the stick when I put it into the tank in order to scatter the worms. But doing that will harm the fish with the stick, since when they all come to snatch the food, they will all be wild and enthusiastic. I have been thinking how to solve this problem for a long time and the use of a small dropper is the ideal solution. (A DROPPER is not a turkey blaster. A turkey blaster is a huge thing used to blast big fat turkeys. And it is not even a turkey baster. A dropper is a miniature version of a turkey baster, if you will).
By the way, I am interested to scatter the worms finely rather than see the fish gobble from a lump because I think that how they eat is as important as what they eat. As an analogy, swallowing a chunk of meat is very different from savouring it properly.

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