Backyard Aquaponics
A place to discuss aquaponics

Hi All,

I'm new to aquaponics and was hoping someone could offer me some advice.

I'm setting up a small new hobby aquaponics system using this kit, https://www.theaquaponicsource.com/shop ... cs-system/

I setup the system with RO water that originated from my well. All the water quality parameters looked excellent. I patiently cycled the system with ammonia, measuring the levels daily. After a few weeks the system handled reducing 1.0 ppm ammonia to 0 after a day. So I introduced 15 Mozambique tilapia fingerlings. I've also planted bok choy, basil, celery, cilantro. The plants are growing like crazy, but have yellowish leaves, indicating low nutrients, I think. All went well, for a few weeks although the fish hardly ate any food. The food was fingerling food I acquired from the fish supplier, https://www.liveaquaponics.com. They weren't excited when I fed them, a few would cautiously nibble, but that's all. Then I noticed that a few of the larger fingerlings had white "poo" strings. After a few days the first fish died. Then another, and another. Now I'm down to 3 fish! Water quality parameters all look excellent, ammonia and nitrite are 0, nitrate is low, temperate is 80F, EC has slowly climbed to 0.4. The only odd thing is that pH has slowly climbed to 8.0, from the original 6.7 of the RO water.

I'm guessing the white "poo" string was an indication that they may have arrived with a bacterial infection or worms. Either that or they are slowly starving.

Anyone have any clues or ideas about what I could do? I'm worried the last 3 will die and I'll have to start over with the fish, but I don't want a repeat of this first die off.

Thanks for any help!

That pH is fine for Tilapia.

R.O. water and even pure rain water, are not good for fish. Your water is probably way too soft.

If you still have fish in the system, the very first thing I would do is add sea salt at 1gm per litre. I would then change out 30% of your system water with some of your well water, or tap water that has been aerated for 24-48hrs. I would repeat this every day, for 3 or 4 days, ensuring any top-up water is also salted to 1gm/Ltr.

Thanks so much for the advice. I added salt to 1 ppt and then did a water large change, adding spring water instead or RO water. That brought the alkalinity way up to 112 mg/L CaCO3.

My well water is off the charts super hard. That's why I used RO water to initially fill the system. In hindsight I should've realized that RO water would be the opposite extreme.

I have one tilapia left of the original 15. He already seems to be looking better. Hopefully that was the issue and my next batch won't suffer.

Where did you get the RO water from? 4 stage RO water is fairly acidic (0ppm PH 4-5).

If it really was RO water, how did it sit at a PH of 6.7? & then went up to 8 .
Something must be causing that to happen.Maybe that's the problem.
How quick did the PH jump up?

Alkalinity? meaning KH?