Another Growbed Needs Attention

The black tub, where those Asparagus been grown need some redoing. Since I have some free time today I decide to redo it. I did place that Stevia Rebaudiana in this tub yesterday as a temporary placement.
As usual, all plants out and all pebbles needs to make an exit too.. :(  About time I make improvement to my Aquaponics setting, as time goes I learn a lot but to make changes do takes time since its hard work.

What needed are.
  1. Additional Pebbles to make it 12" Growbed.
  2. Better Lumber support for above requirements.
  3. Siphon retrofit to smaller outer strainer having use the 32 ~ 25 mm reducer.
  4. Improve "Whistler" on the outlet
Its a bit hard work, but it worth it in the long run.
Since Asparagus need to be removed, above photo shows its roots.
A better close up of same.
Asparagus aside in this basin for the next few hours.
This was the old type of strainer, where there are holes even on top of the pipe. Later strainer I only do bottom 20 ~ 30% of it. More holes on the top is bad, roots invasion may occur.
I'm changing this to the smaller diameter strainer and inner bell will be 50mm/2" PVC pipe as above. Standpipe and strainer in place, waiting for sealant to dry.
Let's not forget the outlet, these can be taken as the rear end of this siphon. We tend to forget the rear it is just as important as the front, at time it may be more critical to have the rear install correctly.

These growbed was almost 2 years old and at that time I was still experimenting with my siphon to make it better. The outlet use was the "whistler" like the one here but not as polished as this. It was made after alteration after alteration and finally this above what I will use for my set up. These four growbed that I have, slowly I'm making a better siphon for it. 
Pebbles from the growbed, not enough more needed. These was from the time when I was experimenting with pebbles size. Those smaller aggregate are not suitable, on average I recommend 10 ~ 20 mm in size.
Pebbles in.
But its not enough, will get few more bags. Pebbles should reach at least vent cap lower height.
Got few bags of pebbles and all done, the Stevia plants in and Asparagus will be later this evening.
This growbed is next, the wooden support also showing sign that it would call it the day any time soon.
But its so much growth on it, that I am reluctant to do any thing to it.. I may have no choice but do it. 

Another thing about redoing growbed is, its best to do it one at a time over a period of time. This to prevent ammonia or nitrate spike since not many plant left to use it up.