I'm going to disagree with Ch4rlie for this instance in one particular case, and agree with him in another...
1 - Goldie will be just fine in this case. The 'seasoned' powerhead for the tank appears to have ceramic media in place, and I assume this is ceramic media from one of the other tanks - hence the 'seasoned' bit of the discussion.
2 - One little goldfish in a tank that size (55 gallons) isn't going to create much ammonia at all, so the 'seasoned' bacteria in the powerhead will be more than sufficient to deal with the minimal ammonia production of that goldfish in a tank that size.
BUT...in this case, Goldie's efforts on your behalf will do very little, if anything to really establish that tank. The tank will be very rapidly, if not immediately, cycled for the bioload of a single small goldfish. I would assume that you are planning to have a far larger stocking in the future. At such time that you add the increased bioload, the tank will no longer be cycled (or even close to it) for a massive increase in the bioload.
Goldie's purpose here is basically to seed the tank with some waste product, which should help develop a little more bacteria than the tank would normally have during a fishless cycle, but ultimately, the bacteria colony for ammonia, nitrite, etc. are not going to be robust enough for a 'full tank' stocking in the future. Goldie is merely providing some ammonia to keep the current bacteria in the filter going... and little more than that.
I would recommend, regardless of your future use of 'established' media, substrate, etc. that you complete a 'test' with an ammonia dose of 3ppm to determine how close to cycled that volume of water really is for a full tank load of fish - WITHOUT Goldie in the tank, of course. Using more established media, substrate from an established tank, etc. will greatly reduce the time, and if you use enough of the material from other tanks, can even fully cycle the tank for any number of fish without a whole lot of time. But, a single fish in there right now means that the tank will only be cycled for that small little bioload. So... right now, nothing of any substantial benefit is really taking place in the tank.