Mixed Gender Tilapia

[benjamin.w.jordan]

Hi - first time poster.  I have a indoor/basement tote-ponics system from the DIY video that has been running nicely and its about time to add fish.  I have been looking at the different tilapia dealers and many are touting the benfits of buying mixed gender pure breed fish.  I've heard placing a simple net at the bottom of the tank prevents the firtilazation process and any eggs will just flow through the system or the other tilapia will eat them.  Is anyone doing this in a DIY system?  Any thoughts on how to place a net at the bottom if there is already water and drain running in the tote?  Or should I just go with all male cross-breed?

Thanks!

Ben

[Jon Parr]

I haven't tried it, but if I were to use a screen to separate the fish from the floor, I would make PVC hoops with stilts and zip-tie plastic mesh to them. And use several such panels to cover the floor like tiles so that I could service an area without disrupting the whole tank. Another means to the same end is to throw a predator in there, like a bluegill, or mosquito fish. They'll take care of the fry, and you can always separate a brooding female if you want her to hatch a batch.

[benjamin.w.jordan]

That sounds like a good idea.  What size holes in the netting would you use to safely let eggs and waste fall through?

[matthew ferrell]

The eggs don;t fall through, tilapia are mouth brooders.  They only spit eggs if you mess with them.

[matthew ferrell]

All male group will grow faster because there body never switches to reproductive growth.  It's all somatic growth.  I do not know who is selling you the fish, but mix breeds are not sterile nor all males.  Mixed sex populations are notorious for having huge size ranges and smaller fish.  This is because the boys get horny and stop using energy to grow and instead use it to hit on every female in the tank.  When females have eggs i their mouth, they don't eat.  There are two ways to go to an all male population.

First, which is the easiest is hormone addition to the feed.  This is feed the first few weeks they are alive and it switches females to males essentially. 

The second option is way more complicated, but works realy well for making huge populations of all males.  Essentially, in this route you make a super male (YY) and everything he produces will be males.  You can look it up if you are so inclined.

[Jon Parr]

There is a third way to have all males, Matthew, and this easier and more healthful in my opinion than sex reversal or super YY males. It is using the all-male first generation hybrids of certain pure strain parents. Some tilapia males have dominate genes, so regardless of which chromosome they throw, the offspring will be male. And yes, they are fertile, NOT sterile, but they are all male. Because I'm in Cali, I use pure strain o. hornorum male matched to pure o. mossambicus females, producing all male fry sometimes called pennyfish. This is the only all-male producing combo legal here, but other states can add blue males and Nile females, producing hybrids called chocolates, and Florida reds, and rocky mountain whites. Kellen can tell us more. If I can find a chart I'll post it. 
The YY male is fascinating, but it is the product of hormonal treatment, which is not necessarily bad, depending on your personal stance, but isn't required to produce all male offspring, so why bother?

[Jon Parr]

IF the eggs don't fall through, they will be snatched up and brooded. But they do fall through. Even mouth brooders can't magically transport from the oviduct to the mouth. The eggs must first be laid, and they sink like stones, the male spreads milt, and then the female sucks them up. The process takes only a few seconds, and is repeated over and over again, sometimes for hours. I think it was TC who said she had babies produced from a few eggs balancing on a PVC pipe long enough to be scooped up. So, not a 100% way of preventing babies, but mostly effective. And the slow growth during courting is not interrupted as Matthew mentioned. I swear my breeding tilapia are shrinking, not growing.


matthew ferrell said:

The eggs don;t fall through, tilapia are mouth brooders.  They only spit eggs if you mess with them.

[matthew ferrell]

Jon I was unaware of that hybrid option.  Thanks for the lesson.

[TCLynx]

I would make the net bottom actually a Cage that all the tilapia are in.  Make the mesh size about 1/4"  Keep the bottom a few inches off the bottom of the tank and the top edge above the top of the tank.

[benjamin.w.jordan]

Thanks TC - do you have any pictures from when you did this by any chance?

TCLynx said:

I would make the net bottom actually a Cage that all the tilapia are in.  Make the mesh size about 1/4"  Keep the bottom a few inches off the bottom of the tank and the top edge above the top of the tank.