Baby Guppy Help?

Hello!

I have a breeding trio of blue moscow guppies in a 10 gallon tank. I was in the process of switching substrate/ decorations (moving from plastic decor to live plants) when this happened.

After I was done re-planting I added all my fish back in. There was some plant debris moving around and I was just watching them react to their new environment out of boredom and noticed a tiny baby Guppy swimming in between the rocks trying not to get eaten.

As quickly as I could I scooped him up in a cup and transferred him into my floating guppy breeder. He is TINY, only about a centimeter long.

For these guppies I was planning on the "Survival of the fittest" method but all the rest of the babies got eaten up because there was no place for them to hide.

My water chemistry is doing fine and my fish are all healthy. How big does this baby have to get before I can ensure that he won't get eaten in the tank? Thanks!