This Week in Sen Sok : Bringing Fish to the System

Fish play a key role aquaponics. They are the first essential living element introduced when starting a new system. Aquaponics, just like any other ecosystem, depends on the nitrogen cycle to convert nitrogen into available nutrients. Ammonia, a bi-product of the respiratory and digestive processes of fish, is the catalyst that starts the “cycling” of our system. As the fish breathe through their gills and excrete waste from their digestive tracts, the ammonia will build up in our aquaponic system. In high concentrations ammonia will kill fish. Thankfully, the presence of ammonia attracts the nitrifying bacteria that we need to cohabit our aquaponics system. The first of which are called nitrosomonas. The nitrosomonas will convert the ammonia in the water into nitrites, which is still toxic to fish. No need to worry though. Good news is that these nitrites will then attract another nitrifying bacteria called nitrospira. The nitrospira is the bacteria we are really after because they are the ones to turn nitrites into nitrates! And plants love nitrates! Nitrates are quickly absorbed by plants, making the excretions from our fish the perfect fertilizer.

So as the week goes by we will watch our water testing spike from high ammonia levels, to high nitrite levels, and finally to a nice and high nitrate level. This will be our indicator that our system is fully cycled and it is time to bring in plants! Once we introduce the plants we will have a complete closed looped system; where our fish are excreting their waste, the nitrifying bacteria are converting the ammonia, the plants are acting as a bio-filter uptaking the nitrates, and the clean water then returns back to our fish.

This week we brought in about 50 locally sourced Red Nile Tilapia to our first family village system in Sen Sok. One step closer to bringing valuable nutritious food to the people in rural Cambodia. Don’t miss our next update as we are excited to come back next week with plants to complete the system!

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