Welcome! You'll want to read-up on establishing a proper nitrogen cycle. I doubt you have any going on unless the filter you have running in that tank came from a healthy, established tank and was kept wet during transport/setup.
Not that I'm the stocking police, but the most you should do in a 29g is two fancy goldfish. Any more and you'll need to do several large water changes per week once they grow.
Even 2 goldies is a bit heavy in my mind but I prefer to keep understocked tanks. Make sure you have really good filtration. And ditto on learning about the nitrogen cycle if you are not already aware.