Bad Luck From The Survivors

A while back, I had difficulty raising my spawns. Thus, I end up with only one or two fry only. It is fairly recent (during the summer when it was not rainy yet) that I was able to increase the size of spawns.

Why "Bad Luck From The Survivors"? In bad conditions, there will only be less than a handful of fish or fry left. There is little chance that you can find a suitable pair especially with obviously one or two survivors. Also, the spawn could be huge but with a strike of bad luck, they are all males or all females. Although, this second incredibly unlucky scenario has a small chance of occurring but it still happens. Then, the continuation of the line is now a problem for the breeder.



So, the breeder is faced with three options:
1) Do an outcross - using a breeder that has no shared ancestor from the fourth generation and farther back but this will only dilute the line, introduce more variables and lose some of the progress made (the fixed characteristics). However, "hybrid vigor" and fertility is increased in the progeny. This can be simple as doing an outcross for a line experiencing no "bad luck from the survivors".
2) Do line-breeding - this is better because the remaining fish will be paired to a related fish, but it is not always possible to have a related line available. Same ancestor at the first two generations will give the best results.
3) Do back-crossing - Back-crossing is crossing the offspring to the parents. In my opinion, this would be the best option. The line will not be diluted and it will actually lead to the fixing of the line since there will be less variables.

Then, going to Option 3: The goal is to raise the fry to adulthood before the parent becomes too old to mate. This might not be a problem to fish with longer lives (like angelfish, flowerhorn, goldfish, etc.) but it is a challenge to shorter-lived fish (like bettas, guppies, etc.).

The breeder must now work to win this race against time.
1) High quality foods. Offer live foods twice or thrice a day if possible.
2) Daily (or every other day) water change. Minimum 50% but it can be a 100%
3) Any exposure (not necessarily in the same tank but the tanks of the two are beside each other) between parent and offspring. This will help the breeder gauge if he can accelerate his plans sooner or wait a little longer to grow his precious fry then breed them.