Symbi Biological

Aquaponics Filtration Improvements

​​​We made several changes to the aquaponics filtration system. Here’s a video showing the full scope of the new components added. I will have individual posts of the components to share the details of what we did and why. If you have any questions, please reach out to me at

Aquaponics Filtration: Settling Well


Well that settles it. At least, I hope it does. We are upgrading the aquaponics system to improve the filtration part of the system along with some other minor changes. It seems like the Settling Well design is the way to go for the first step in our filtration. In our first design, we used a baffle in our clarifier to settle the solids, but it never really performed the way we had hoped providing the humorous observation that it provided “baffling clarification”—meaning it didn’t work very well. My guess is that the solids would settle, but some of the finer solids would then get picked up by the flow of the passing water, so it never really worked the way we wanted. It filtered, but also sort of unfiltered in a way. With that observation, we pulled the baffle out of the 250 gallon cone bottom tank to change over to a swirl filter design. This was an improvement, but still not performing ideally. I imagine both technologies are valid with proper engineering, but we were copying what we saw elsewhere and figured it would work.


Barrel inside the cone bottom tank. Inlets bring water here to settle.

When redesigning our aquaponics system, it was important to reconsider the radial design and look at something else. We decided on the settling well design after consulting with Huy Tran and it is doing pretty good job as the first line of filtration. Just for the simple fact that the turbulence within the cone bottom tank is now minimized allowing solids to truly settle. As the system redesign is completed, I will share the rest of the changes and look forward to seeing how they perform.


Pulling out net pot inside one of the two skimmers that take the water to the next step in filtration.

Volunteer Integrated Pest Management—Ladybug Larva

We’ve got some aphid eating volunteers visiting the aquaponics greenhouse for the third year in a row. This video is of a lady bug larva on one of the lettuce leaves. They like to eat aphids and other soft bodied sap sucking insects you may find in your greenhouse. You’ve probably seen ladybugs for sale at your local nursery as part of an Integrated Pest Management program. If you’re lucky enough, they might show up for free depending on where you live! Our region near the California coast seems to be a particularly attractive place for them. The University of California Agricultural and Natural Resources says the adults typically over winter somewhere cold like in the Sierra Nevada Mountains. The cool temps lower their body temperature slowing their metabolism so they can live off their body fat until it warms up. In Spring, they head west to the coastal and valley areas of California to find food and eventually lay eggs. It’s always interesting when they find the greenhouse. There is rarely a shortage of aphids inside! I wish they would stay for longer, but they usually leave after a short stay. Lady bugs are great for integrated pest management, but you should always consider that they do look for greener pastures fairly quickly. That’s why I tend not to buy them for IPM since it seems they stick around for only a short snack and then go looking for something else. That said, they’re always welcome to a feast anytime they find us. Bon appetite! Or, should I say, Bon aphidtite!

Aeration and Crud


Aerating your deep water culture beds is a really good idea for more than just the obvious reason of keeping your plant roots healthy—it also helps keep your system water clear. Introducing oxygen to the trough sustains healthy root development in the aqueous conditions with ideal levels being at about 8ppm of DO or dissolved oxygen. The plants will grow at lower levels, but so will other things potentially opening up your system to disease and other issues. Clearly, healthy plants mean a better harvest with fewer pests and a more natural disease resistance. But also, from a food safety perspective, keeping the beds active and moving is a better way to ensure there aren’t pockets of anaerobic sludginess building up in your system. The sludge buildup can cause a host of problems from increasing BOD (biological oxygen demand) of the system to physically covering your roots and essentially suffocating your plants.

We often focus on the fish as the reason for the filtration in the system, but the plants also have a role when it comes to suspended solids production in your deep water culture troughs. That’s why it is vitally important to aerate your system beyond just the fish tanks. As plants grow, they slough off root cells and produce root exudates through photosynthesis feeding bacteria which grow in the system troughs. Without some form of turbulence in the trough, the organic matter will continue to build up away from the primary filtration in your system.

In our experience, airstones placed every 4 feet in the deep water culture troughs helps to ensure there is enough oxygen getting to the plant roots and also provides enough turbulence to suspend the solids, which will eventually be captured by the filtration to keep your water clear. 

Keeping the crud out of your troughs allows you to keep a consistent DO and assists the beneficial biology to stay healthy and do their jobs more effectively providing more nutrients for your plants to grow healthy nutrient dense produce. When designing or redesigning an aquaponics system, make sure you remember to aerate your troughs.

Microbial Ecology of our Aquaponics System

NASA syringe sampling

Angela Detweiler takes sample. Photo by Sander Van den Groenendaal

Learning more about the microbes in our aquaponics system and how we can improve or encourage those actors to do their jobs more efficiently has always been a goal of the Symbi Biological program. Put another way, we’re talking about the microbiome and microbiome eco system services that are performed. We know that there are certain nitrifying bacteria doing most of the heavy lifting in aquaponics, but what others are present and what role to do they play in nutrient cycling? 

We volunteered to provide samples as part of a very exciting NASA study of the microbial ecology of food production systems. Scientists from the Microbial Ecology / Biogeochemistry Research Laboratory at NASA Ames Research Center will determine the


Photo from

microbiome of our aquaponics system Read More

Measure to Manage: Nutrient Analysis #5


Every so often, I post our nutrient analysis of the aquaponics system water using a Hanna photometer. In the last 6 months, things have been fairly consistent except for the winter months. As the system temperature dropped below 57F, the nitrification slowed somewhat and the nitrite level jumped significantly. I think this was a result of both the cold system temperature slowing down the bacteria and a catfish tank that had fewer fish than I thought. Fish food was collecting in the tank and probably contributing to the nitrite issue as a result. I had been concerned that the catfish were not growing and decided to empty the tank to see what was going on in there. As it turns out, the catfish were almost the same size as when we started last year! Read More

Wormery Frogs Evicted


Last year, I started to notice an increase in Pacific Tree Frogs in the Wormery. At first, they were cute, but I did notice that my integrated pest management team of spiders and other critters of the worm bin were slowly disappearing. Back when I started the worm bin, we had a diverse group of insects and invertebrates. So many that it compelled me to make a video called Critters of the Worm Bin where you see all of the major players in a worm bin from a worm’s eye view at 10x and 15x magnification. Filming a pill bug eating a worm is still one of the coolest things I’ve ever seen.



Then about a year ago, it became obvious that making that film again would be next to impossible since most of the critters starring in their roles had disappeared. I don’t think they were on strike. They were gobbled up actually. Slowly, the frogs were beginning to take over the worm bin. Reluctantly, I’ve been gently relocating them outside where they belong. When I first noticed them, I figured they were eating some of the worms as I mentioned in a previous post. Upon further observation, I think they were eating a LOT of the worms! Not exactly surprising, but if you see frogs in your worm bin, I’d suggest showing them the wonderful natural habitat they already have or you’ll be raising frogs like me. And making fish food from frogs, well, I’ll leave that for someone else to try!