Tilapia Breeding @ lower pHs

[Wayne Tajiri]

Aloha Everyone!

May I please get some input on this matter?  We have had our aquaponics systems for about 2 years now. 

1  - 600 gl Fish Tank overflowing into:

8 - 55 gl barrels cut/filled with black cinder for bio filters, parallel connected to a single bell siphon, draining into

3 - 4' x 20' troughs, daisy changed, and overflowing into

2- 300 gl Rubbermaid containers in series as the sump, containing the water pump back up to the fish tank.

2000 gl water, 100 lbs of blue tilapia

My issue is the breeding.  Since we keep the system @ pH 6.3- 6.5, I notice that we have not had much breeding activity.  We had some last year, during a period when I was very busy and had not noticed that that system pH had crept up to about pH 7.8.  All the plants were dying, but the tilapia were doing good, feeding well, and then we had a couple of batches of babies.  I pushed the pH back down, and it seemed like the breeding activity had stopped.  It was kind of late in the season, so I thought that it might have been water temp, but in hind sight, I think that it may have been the pH.

Can anyone tell me if the tilapia stop breeding if the pH of the water is down around 6.4?

Mahalo for every ones  input . . .

[Jeff S]

I'm not sure what the best breeding ph is. I know temperature has a lot to do with it. My PH is 7.3-7.4 an breeding isn't a problem. My water temp is 82. Hope this info helps a little.

[Wayne Tajiri]

Aloha Jeff S!

Thanks for responding.  I think that that is part of the problem.  7.3-7.4 is good for tilapia, but not good for plants.  Tilapia still grow well @ 6.4-6.5, better for the plants, but I'm beginning to think that they stop breeding at that low of a pH.  Just wondering is anyone else has had this experience.