Outdoor System Launch 2011!

In the first week of May I completed the initial setup of my outdoor flood and drain aquaponics operation. I grew outside for the first time last year, and I’ve made substantial alterations to the system design based on my experience (click for diagram of old system). This year, I’ve replaced my old shallow, clear plastic grow beds with 55 gallon blue plastic barrels cut in half lengthwise. I’ve also replaced the ¾ inch gravel with ¾ inch expanded shale (from Rob Torcellini of Bigelow Brook Farm). Lastly, I’ve installed an autosiphon to flood and drain the grow beds, based upon the design from Affnan.

Grow bed with expanded shale and autosiphon viewed from above (left) and below (right)

Grow bed with wood frame and cement block stand

The updates to the system should prove fruitful. The grow beds are now a 12” deep in the middle, about three to four times deeper than last year. This will allow for much longer roots, more surface area to absorb nutrients and water, better insulation from the heat, and greatly increased area for nitrifying bacteria growth. I’ve switched to expanded shale for its light weight, moderate price, and pH neutrality. The autosiphon provides me with a failsafe method to flood and drain the grow bed – no moving parts and no possibility to overflow.

Still using the 160 gallon plastic fish pond, I’ve set up three barrel halves for a roughly 1:1 ratio of tank to grow bed volume. The barrels are all connected with 2” PVC pipe and use one autosiphon at the opposite end at which the water will enter from the pump. Hopefully one siphon will be sufficient for the system.

Given the short growing season in New England, plus the time delay needed to cycle the system to build up nitrifying bacteria, I’ve decided to try a fishless cycle. Without fish, I can put pure ammonia into the system and achieve much higher levels of ammonia than the fish could tolerate. With ample ammonia, I hope that the nitrifying bacteria will establish and multiply relatively fast. Unfortunately, the one key ingredient the bacteria need – heat – is seriously lacking this month. The bacteria flourish in 75-85^oF temperatures, and May has delivered cold, wet weather.

Meanwhile the fish are happy inside feeding some chard and tomato and pepper seedlings! See next post for more on that. Also, there are three more barrel halves that I plan to turn into additional grow beds soon.