Tilapia Color Change

[Jeff S]

I have 2 IBC tanks, 1 with 800 fingerling Blue Tilapia and the other with my 5 original breeders and a few sample sizes of several different litters of fingerlings. The tank with the breeders basically acts as a sump with a makeshift radial filter from the fingerling tank inside. Today I put some fish in the sump that were from the same litter as a couple that were already in there and I noticed that the ones I had left in the sump were larger and were a brownish color as compared to the new arrivals which are dark grayish. The other larger Tilapia and the smallest ones in that tank are also brownish but growing well. Does anyone have an idea what might be causing the brownish fish color and the better growth in the sump tank? 

[Jeremiah Robinson]

The size difference could be food competition.  In tilapia, the more aggressive fish eat a lot more than the more passive fish.  So a single fish could grow three times as fast as another, depending on how aggressively they compete for food.  That's actually an advantage if you want a high stocking density and continual harvest.

I haven't raised blue tilapia, so can't speak to color.  Have you found that they have good growth rates?  I've heard blues are slower than the Nile ones.

I hope you're planning to sell some of those fingerlings before they get too big :)  800 is way too much for one tote.

[Jeff S]

Since the post I noticed that the new fish I added to the sump also turned brownish but seem healthy. The aggressiveness wasn't an issue. The size difference was from tank to tank plus I don't know how many male/female I have. I'd love to sell some just to thin the herd. I'd hate to think I have to just dispose of some. BUT I do have more tanks.

[Jim Joy]

My blue tilapia change color from a light pink (males looking for love) to silvery to dark banded (females ready for loving) to almost black (don't mess with me).  I've seen all of these color variations in the same individual fish.  When I quarantined a male that was too aggressive - injuring the females - he went from pink with red edges on his fins to dark banded vertical stripes.  Amazing fish.  

[Jeff S]

I thought the red finned fish was female. I had one that was acting aggressive but the way females do when protecting eggs/fry and it wasn't eating, another characteristic of a brooding female. I attempted to separate it from the others without success but the activity seemed to scare the color out of her/him but it came back later.