I have just finished my first cycle of growing tilapia. My tank is 250 gallons. The system was set up a year ago with 50 fingerlings consisting of various varieties.
As the fish grew, I noticed that there was a very pronounced difference in growth rate. After a year, some were almost 11 inches while others were closer to 4.Since I wanted to harvest the fish as a batch, so that I could restock with more fingerlings, some of the fish didn't provide much "meat".
My system is in my basement and is heated to about 75 deg. I feed the fish 2-3 times a day, and they seemed to eat everything I put into the tank. I supplemented the dry food with red worms about once a week.
So, here are my questions for the forum. If I harvest only the larger fish and eat them fresh, not frozen, will the smaller ones grow up or are they stunted?
Next question, is it usual to have a large variation in size, or am I doing something wrong?
I believe it is normal to see varying growth rates between different sub species and then between males and females within. Even within the same sex, same sub species, growth rates can vary due to genetic variation. It would be interesting to do some controlled breeding for growth rates but when I suggested that to an acquaintance of mine, he said "they're fish, not race horses."
If there is no competition for food, there should be no stunted growth so as larger fish are harvested, the smaller fish should continue to grow. The smaller fish were probably females or mostly females. When I feed, I try to put in as much food as they will consume, with the idea that stunting will be prevented.
You could heat your water up a bit more and let them breed, dipping out the fry to a separate tank, such as a small aquarium. It might be relatively inexpensive to heat the water to 85F or so during the summer with PH 8.0 or thereabouts.