From what I remembered, this thread has not been updated for awhile, so I will answer some of the questions before the owner jumps in.
At what age do the stripes actually get the so called gold?
At least 2-3 years before you even see the slightest yellowish tint, I have not seen any t.r. GSM that reached the w.c. GSM complete yellowish/gold color yet. It seems that it is either missing something in the captive environment or it just takes a long long time. Typical breeders need to hold these GSM stock for 1.5 - 2 yrs before they can sell, and there are alot of fighting (causing deformity); not the best sellers for breeders.
And at what age are they capable of breeding?
Do not have definite answer, but from what I read, at least a minimum of 3-5 years.
Will GSMs spawn when they are living in pulsing xenia?
yes, as long as they feel comfortable. However you might wanted to provide spawning media for easier removal (i.e. pot or tile)
I know that the next questions will most likely be covered later... but still want to ask now.
What type of filter is the best to use for a fry tank?
Depending on the tank size, sponge filter to totally no filtration (daily water change from the parent system) can be utilize. Sponge filter for too young fries might actually kill them because the bubbles lift them up, making the fries hard to swim.
Do the parents need to be tranfered also?
no, parents will eat their young once they hatch
Food... Reading and listening to people on what to feed fry gets me all mixed up. Are you going to go into and possibly list what foods are needed at what point and how to make them?
If you are looking into breeding, you will need rotifiers & baby brime shrimp. You should have a stable culture of rotifers (and its food phytoplankton) ongoing, once that is stable and concentration is at a high enough stable concentration, you can start to rear the young.
My suggestion if you really wanted to pursue the breeding game is to take a look at Joyce Wilkerson's book "Clownfish"; it's known as the clownfish bible among the circles.
good luck