Backyard Aquaponics
A place to discuss aquaponics

Hi Guys

My PH is around 7.8 and over the last week I've added about 40mls of Hydro Acid to no affect.
Now I'm guessing its because my water source is from my new concrete water tank.

Is there some thing i can keep in the FT to bring the PH down ?
Also do you think it IS the Concrete storage tank causing the PH to stay hi ?

Thanks

How long has it been at 7.8 for? Personally I would just leave it if it's a relatively new system, it will come down over time and topping up with small amounts of higher pH water doesn't have any negative impact in my experience.

Do you have any fish yet?

30 fish....
been up there for as long as its been running , 5months or so. Plants are struggling

I too have high ph source water. Lots of limestone in our area.
Only thing that's worked for me is to add hydrochloric acid or I believe more correctly, muriatic acid.
Add it to an external source like a spare 220 liter barrel. Test that water after you've dosed it. Depending on how much water this is being added to, will affect how low you want that top up water. My system has been running for almost two years and I constantly struggle with high ph.

You're right it causes minerals and nutrients to be locked out of the plants. Good luck.

It is possible that the concrete tank is causing problems but it could be something else like naturally occurring carbonates in the water.

Iron is likely the main problem nutrient. You can spray this on and avoid the pH lockout of the system water. Something like Maxicrop plus iron works or you could also get some Fe-DTPA chelate and use this. The iron chelate will also work if added to the system water because it is plant available at a higher pH.

Chelated Iron - 1 level teaspoon per 1000L every 6 to 8 weeks if pH is above 7.0 and iron deficiency is indicated. Fe-DTPA is light sensitive probably best to apply just before dark (about 96 hours for >90% of Fe-DTPA to be destroyed with exposure to light of the wrong wavelength - usually precipitates out and becomes unavailable to the plants). http://www.ars.usda.gov/SP2UserFiles/person/11847/albano_miller_2001_Hort%20Sc%2036%282%29_%20pp313-316.pdf

If you post some pics of the plants and system we might see what else is going on and be able to offer a few other suggestions .

The concrete basically has masses of lime in it naturally, it's one of the major ingreditents of it. So you're going to have a high pH until the lime stops leeching out of the conrete. I have no idea how long that'd take.

Follow Scotty's advice on foliar spray if you're getting colouring problems on the leaves, at a high pH, you'll run into trouble with the plants taking up what they need.

If the concrete is just a storage device, and no fish inside, you can try an old koi tank trick.

Pour enough hydrochloric acid into the tank, so that the pH is brough right down to the 6's, and keep it there, by continually adding more acid. The acid will eat away the lime in the closest layer of concrete, and it should stop leeching/high pH. If there is no fish, you can swing the levels around all over the place.

But a small amount of carbonates/lime isn't bad for the system, it'll depend on your system size/stocking rates, but it'll stop the pH from crashing like many systems, and you won't need to keep on adding things to keep it up.

You didn't say if the concrete was sealed or not. Raw, unsealed concrete leaks like sieve, so I can't imaging it not being sealed. If it is not sealed that most definitely is a contributor to high PH, no question. If it is sealed then it is most likely your water source. Test it. High 7s to low 8s is normal for water running through limestone. If you are wealthy, an RO system is the best thing you can do.

I have the same problem because of my water source. I have been doing aquaponics with Tilapia for 7 years and I still have not found a permanent, easy and cheap solution. I am not wealthy so, I am considering using an oak leaf mulch in mesh bags under a layer of my expanded shale grow beds and see if that can help. My system is 600 gal recirculating flood and drain system with about 24 sq feet of grow beds. I am told that more grow bed area could help as the nitrification process actually lowers PH as well. The problem with that is I am limited to the area I am able to use.

Does anyone have experience using a mulch layer to lower PH as I described above?