Okay! I finally got what I needed to rebuild my filtration system. The changes I made weren’t major, but hopefully they will help avoid the problem of the system backing up and overflowing like the old one.
This picture is a bottom up view of the biological filter bucket, with larger holes in the bottom and a screen in front of the holes to filter out large particles that were not caught by the swirl filter. The previous filter didn’t have a screen and the holes were small, meaning they got clogged more easily and were still big enough to let large particles through. Hopefully this filter will work better.
The next picture shows the new swirl filter. The previous one had the inlet higher up and pointing only in one direction, which meant the swirl action wasn’t very strong. A lot of large particles failed to settle at the bottom. I also put the swirl inlet at the bottom to force the particles to stay down there. This is a popular swirl filter design I’ve seen on Youtube that seemed to work well for people.
Here is a wide shot of what the set up looks like.
The first iteration of the aquaponics system appeared to work at least in terms of the flow rates matching. I used a 250 GPH pump, which matched well with the 1/2″ PVC inlet and 1″ PVC outlet. It appears to be important for the outlet to be at least twice the diameter of the inlet to make sure the drainage can keep up with the pump. The biological filter, pictured above as the yellow rectangular bucket, was filled with a layer of activated charcoal on the bottom and 200 bioballs above it. Below the activated charcoal I drilled five 3/8″ holes for the biofilter to drain slowly into the tank, aerating the water from the splashing and providing biologically filtered water.
The reality of the system was that I needed to have spent more time allowing the biological filter to establish. 2 weeks was not sufficient. According to the United Nations FAO Fisheries and Aquaculture Technical Paper, it can take at least 3-5 weeks to establish a healthy culture of nitrifying bacteria to effectively clear the ammonia. My system became overwhelmed with waste after a week of running.
It’s possible that this system would have worked if I had waited longer to establish the culture. My next system will have a slightly modified swirl filter made with a better bucket (the reused paint bucket leaked due to the ridges at the top so I need to find a bucket without ridges – the bulkhead adapter did not fit flush with the side of the bucket.) Another modification I’m making to the swirl filter will be that the waste inlet will be at the bottom of the bucket instead of in the middle, and I will add a screen a few inches from the bottom in order to make sure the waste stays at the bottom and does not coat the entire bucket. This is not necessary with small amounts of waste, but as I found from my first test – large amounts of waste can easily accumulate while the tank is “cycling.” (Cycling is the term used in the aquarium world that means building up the colony of bacteria that turn ammonia into nitrite and nitrate.)
Another thing I plan to do is “fishless’ cycling. This is safer because it does not involve subjecting any actual fish to the wild fluctuations in water quality that occur when setting up a new system. There are lots of instruction pages online for how to do this, using slightly different strategies.