Why are my two loaches different sizes? Are they different genders?

[pinfish]

Hello, my two gold dojo loaches have grown to be two totally different sizes than each other. Both were purchased on the same day out of the same tank and were originally both identical in size. The larger one is a much deeper gold color while the smaller one is a lot lighter and paler. I was wondering if anyone had an idea as to why one grew so much bigger and faster than the other? I will try and post a picture of them when I get home today. Thanks!

 

[BIG-G]

Could be a number of factors.
Dominant fish will grow larger and faster because as the dominant fish you get the most food the best hiding places and reduced stress.

Could just be better genetics.
If you ever spawn fish you will notice that some of the fry just do better and grow faster.
Typically good breeders will cull these runts and pass on quality fish but when fish are sold really small they haven’t been subjected to the culls necessary.