I should have paid more attention to my science teacher.

You have all heard of a sweet spot?  On a tennis racket it’s somewhere in the centre. It’s that area which gives you the best result for the least effort, something like the 80/20 rule.  Aquaponic systems also have a sweet spot regarding the pH. My system’s pH was in the region of 7.8 and I needed it to be about 6.8.  In the sweet spot the plants have a much greater ability to absorb the nutrients from the water.

So, how do you lower the pH?   The pet shops sell all kinds of expensive potions which generally contain some form of acid. Seeing that we’re all about conserving energy it wouldn’t be economical to do a pet shop visit just for that.  I took the easy option for my kitchen aquaponic setup - I reached for the vinegar.  I popped  a spoonful or two into the growbed and initiated a flood/ebb cycle.  The pH has now dropped to 6.2. Hopefully it will settle in the sweet spot.

I should have paid more attention to my science teacher at school.  There must be some defined volume that would take it to 6.8 . Let me see :- 13 litres water  @ pH of 7.8, final result 13 litres @ pH 6.8, pH of 5%  vinegar (acetic acid) is 2.4. Volume of vinegar needed is ?? - way to complicated. Common sense and some trial & error will have to suffice.

These two photographs are taken one day apart.  It's amazing how much the roots of the plant on the left has grown in 24 hours. (I really need to figure out how to get rid of the reflections.)

If you look closely one can also see the layer of stones between the LECA.  This is to keep the LECA from floating.

17 October 2012 @ 9:43

18 October 2012@ 9:48