I disagree you do not need to pair a sibling pair. You need to buy the best fish you can afford IMO. Quality fish will give you quality babies. People that buy from breeders what quality that's why they go to breeders.
Buy 2 fish that compliment each other. If your females ventral fins are a bit too long look for a male with shorter ones. If your male has a not so gear towline look for a female with a great top line. So when it comes to form always try and get a mate that will help fix the other faults.
As for color it is easy to have an idea of what you will get when you pick 2 fish of the same or similar color. If blue marbles are what you want find 2 blue marbles.
Most important is health. You want active fish that are big and strong. A male that makes a bubble nest is a good sign. A female that flares and is nice are round also good.
Last edited by snowflake311; 01-27-2014 at 11:01 AM.