Silane's method of determining if your shrimp are pure:
isolate a male and a female shrimp in your line. Breed the male with a golden female; if any of the babies are goldens, the male has golden genes. If not, he is pure. Do the same with the female but with a golden male instead; if her babies do not contain goldens you can be reasonably sure she is pure. Then, you can breed those two shrimp together to start your line.
Sound tough huh? You gotta do something like this for every shrimp in order to start a pure line. Most all our shrimp have been crossed with goldens though, especially higher grades. It takes about 5+ years of culling to make something like what Benibachi calls S grade. It's hard work! But kudos to you if you decide to try it.