Cloudy water can be caused by a lot of things, but most things should have manifested in other towers as well. One of the causes we read about was a bacterial bloom, but yeah, what kind?
Then we thought back to the moment when all this started, the same weekend we found human feces next to tower 3. We don't know how it got there, but it was there… And then a totally new possibility opened before our eyes. We also realized one of our team members who worked closely with the system got 'food poisoning'.
Even the slightest possibility of fecal contamination of the system we had to take seriously. Especially a closed system like this, where the water is warm to stimulate bacterial growth and there's no coming-in of clean water. Therefore, yesterday was spent researching and reacting to a totally new situation: how to decontaminate an aquaponics system? Luckily there's a lot of information about situations in developing countries.
This is what we did:
We took all the fish out and put them in a separate IBC tank without grow beds. Already more than ten fish had died and some of them were on the verge of dying. Some had very nasty wounds on their bodies. We added salt to the water to relieve them. This water has to be changed very regularly now, since there's no biological filter. By changing the water, we hope the fish will swim themselves clean.
We took this chance to count them and weigh them at the same time.
Then we emptied tower 3 of water, put clean water in and added thin bleach, a dilution (with water) of sodium hypochlorite, which is used in drinking water as well, although in much lower quantities. We'll let this cycle for a few days, empty the tank again, put in new water and let that cycle for a few days before adding life to it. Chloride evaporates by itself.
We hope we took the right precautions, even if it was just because of a possibility.