Since my last update was not really a full new system, i'll give a little bit of bonus footage.
I did a lot of work with tilapia breeeding during this same time.
The tilapia were breeding in my stock tank but there was no fry cover to protect them and they would usually get eaten by bluegill or other tilapia almost immediately after leaving their mother's mouth.
Occasionally, i would see a few fry swimming at the surface near the side of the tank and i would be able to net out 10 or 12 and put them in an indoor aquarium to grow out.
During breading season the largest/dominant male's head turns red and they stake out their territory at the bottom of the tank. I put a lot of PVC pieces in my tank to segregate it and I ended up with 3 males that were able to make a nest/territory.
The rest of the tilpaia males and females just try to stay out of the way. You will have 3 males taking up 295 gallons and two dozen other fish taking up 5.
I moved 1 male and 3 females into an indoor 55 gallon tank(top). You can see some of the fingerlings i was able to save from the outside tank in the early days of spring. (bottom)
The male is very big for a 55 gallon tank. He thinks the whole tank is his territory and he constantly harasses the 3 females to get away. The largest female was ready before the others so her and the male teamed up to bully the other two. Overnight they shreaded the side fins of the second female and pecked at her until she no longer bothered to defend herself or run away. I removed the smallest female back to the outside tank and i moved the second bullied female to an isolation tank but she died a few days later.
When i came home from work that evening the male and female were finishing up. The female would lay a few eggs in the nest. The male would swim by and do his thing. The female would pick the eggs up into her mouth and lay a few more, rinse, repeat. Once they were done, the male changed and was very aggressive to the female and she was unable to get away. So i moved the male back into the outside tank and left the female there alone.
10 days later i came home to a few hundred fry and a proud momma tilapia. The female has not eaten in 10 days and while she shouldnt eat the fry immediately, eventually her motherly instincts wear off and her survival instincts come back, so i moved her outside and left the fry in the tank alone to grow.
Notice I was circulating water between the tanks with a pump and an overflow, but i had to stop this because the tiny fry were slipping through the overflow into the bottom tank where they became fingerling snacks.
Conclusion. I felt like my 55 gallon tank was too small to breed in. So I moved on to try another method which i will talk about below. However, i have since found out that a 55 gallon tank can be use you just need 5 or 6 females. They will school together for protection and the male tends to be less aggressive and damaging than when he can corner and isolate just one or two. The work required to move fish around in different stages was also a deterring factor. The risk of injuring the fish through handling is also worth considering.
Credit: The following technique was gleaned by reading "badflash"'s posts on the diy aquaponics forum. Not exactly his design but I wouldnt have gotten here without reading his work and information.
I stopped trying to move breeders into my internal tank and just started watching the fish in my outdoor tank. When a female has a brood she will isolate herself. her jaw starts to get bigger and she will not open her mouth. In later stages of brooding, her color changes to dark black vertical stripes that are easy to pick out.
I would net the brooding mother and drop her in a half filed 5 gallon bucket. She is usually scared and will either spit out the eggs, swallow them or (in most cases) a little of both. Once she's in the 5 gallon bucket i pick her with my hands, open her mouth to rinse the rest of the eggs out and then i set her free.
I then incubated the egg's in DIY egg tumblers powered by air stones. (This is my first tumbler design, it's improved some since) The weaknesses of this design is that the air stone is not secured [if something moves the air hose or the tumbler you could send all of the eggs into the aquarium to their eventual deaths] and the base is not stable, it wants to move/float.
A closer look. The very new eggs are white. As they get older, they will start to turn brown-orange. Then a couple of dots shows up in the brown that will eventually be eyes. Shortly thereafter a tail sticks out of the egg. The last stage looks like a tiny fish with a big ball on his belly which will get absorbed over the last couple of days.
If the eggs are still white after 3 days they are unfertilized or dead. They will start growing mold/funguses or be food for the fry that do hatch.
It's a blurry picture because the camera doesnt know what to focus on but you can see a school of fry in the middle (they came from the left tumbler). On the right side, you can see that those eggs were a a day or two behind because those fry still have egg sacks on their bellies.
Tilapia typically breed every 4-6 weeks. I found that if you strip the eggs from the mother early she doesnt seem to use all of her stored energy and she will reproduce again in closer to 2 weeks time. I think one case it was as quickly as 7 days.
brian
