The Buddhist practice of releasing captured animals into the wild to gain merit (for the one doing the releasing) is generally a bad practice. Captured animals are often fatigued or not suited to their new wild environment.
In Buddhist countries animals are sometimes deliberately captured just so practitioners can release them (after paying for them). Clearly, that is a preposterous activity.
Most American Buddhist are aware that thoughtless release does more harm than good, but the basic idea is appealing. Why not save a life if you can?
If you want to save lives without doing any harm, a cat collar might be a better choice than releasing goldfish into the East River (this has happened), where they promptly died.
Here is an article about a collar that seems to work well: Study finds cat collar can save songbirds.
You can get one for your own cat or get a few to give to others. BTW, I have no economic interests in these collars and do not know the people involved in making them. It just looks like an easy way to save precious songbirds.