Aquaponics pH

 credit to:  http://aquaponics.net.au/blog/

The term pH is short for potential hydrogen.  pH is important because it affects plant growth, nutrient availability, elemental toxicity and microbial activity. The pH scale is where we measure the acidity and alkalinity levels for the growing of vegetables.  Most vegetables like a pH of between 6 and 7, where 7 represents neutral.   Numbers below this correspond to an increase in acidity, and above an increase in alkalinity.   The uptake of nutrients and trace elements only occur in certain pH ranges.   Iron, boron and manganese, for example need a slightly acidic pH level for their uptake, whereas nitrogen, calcium, phosphorus and magnesium need a neutral to slight alkaline pH.

Mineral table and pH Image from Green Living.com

Here at Practical Aquaponics we have been keeping records of the PH levels in the different tanks.  In the majority of the tanks the PH levels maintain themselves at around 6-7 PH.

However, we recently noticed that the level in our floating raft tank had dropped down and been sitting at around the 4-5 PH. The fish and plants were all doing well, but we decided it was time to buffer the PH level back up.  A few days ago we added 10 grams of Potassium Hydroxide and then waited 24 hours to check the levels again.  The PH had increased slightly, but on checking the next day it had dropped back down.
This time we diluted about 125 grams of lime and added it to the top tank so that it could dilute itself right down before it reached the fish tank.

Lime working it's way through the Box Filter.

Wow.  I checked the PH as usual this morning and it had gone up a whole 2 points.  The tank is now sitting at 6.5PH.  Yesterday it was at 4.5PH.  What a difference.   And the plants, although they looked fine before, just seemed to have a more green look about them.

One of our other tanks, we call it the catfish tank, was slightly high, about 7-8 PH, and the plants in the beds didn’t look as if they were doing as well as they should be.  To this tank we added about 15-20 ml of  Hydrochloric Acid.

There wasn’t that much change in the PH level in this tank today, but I did notice a difference in the plants.  Overnight, the plants looked healthier.  There was more green growth on the plants than the day before and they just looked more alive.

The one thing that amazes me about the aquaponics system that I have noticed is how fast the plants seem to grow.  From what I have seen since I started working here, the growth of the plants is much faster than planting in the ground.  I have to wonder what this is all about.  I am guessing that it has to do with the nutrient uptake, but will have to look into it more.

I will get back to you on this one.
Contributed by Kerry.
(Kerry is one of our staff members here at Practical Aquaponics)