Why You Don’t Need A Biofilter:
There’s a lot of nonsense about needing “filters and biofilters” in your aquaponics system coming from people who simply don’t understand how and why these systems work. Our LD systems don’t ever have, or need, biofilters! Here’s a metaphor that will help you understand this situation: if you put a cup of water into your tank every time you fill up at the gas station, you can fix the problem by installing a “water filter” in your fuel line, but if you simply don’t put water in your gas, you don’t need a water filter.
(Below) Slimy dark roots usually mean plants are not growing well.
In much the same way, one doesn’t need a “filtration” system, solids settling tanks, net tanks, degas tanks and so on, unless you’ve mistakenly or ignorantly created one of several conditions in your aquaponic system:
- You’re using a cheap fish food, and because it is not well-processed and formulated (it’s a CHEAP fish food, remember?) there are large undigested chunks of decaying organic material passing through your fish and going out into your troughs, then this stuff is coating the roots of your plants out there (we’ll explain why this is a problem in a bit).
- You’re using a good fish food, but are feeding way too much of it to your fish. This is easy if these fish are tilapia, for they have a pass-through digestive system that simply spills the excess undigested food down the “out” pipe if they overeat! As a result there are large undigested chunks of this decaying organic material passing through your fish and going out into your troughs, then coating the roots of your plants out there.
- You have designed or implemented your system with information from an aquaculturist, not someone who is profitably practicing commercial aquaponics. Aquaculturists like filters, because they are the ONLY way you can get bad stuff out of a system that has NO plants in it! Profitable aquaponics practitioners know you can run systems for years without a mechanical filter anywhere in sight; for your thousands of plants are your filter.
- You have WAY too many fish in your system. This usually happens when you have taken advice from an aquaculturist or a university aquaponics department that has never had to make money selling fish at a profit. There’s a problem with this: in most places in the world, the cost for fish food, electricity for aeration, labor to raise the fish, and other costs are MORE than the local wholesale price for the fish. You are probably losing money raising fish, you just haven’t got the news yet. Please have anyone who contradicts me present you with their P&L statement from a profitable fish farm in the US; for there are only two or three that I know of, and they are highly specialized and selling into small niche markets (there are MANY in China and Thailand, but labor’s $4/day there).
(Below) This is how they should look: beautiful, healthy aquaponic roots.
It’s MUCH easier and cheaper to fix this “problem” without a “filter”, once you understand what’s really occurring. Here’s a clear description of the phenomenon that’s causing this confusion:
A digestible fish food results in a slimy, well-digested fish poop that immediately breaks up into micro-micro particles when it hits the swirls of airstone bubbles in the fish tank. All these tiny particles have tons of surface area, which the heterotrophic bacteria that live in your system and break them down into ammonia love. The more surface area that is available for bacteria to colonize, the faster you will get results from that bacteria. The resulting ammonia is what the nitrosomonas bacteria love; they metabolize it and excrete nitrites. The nitrobacter bacteria love nitrites, and metabolize them and excrete nitrates, which looks like nutrients to your plants; they love nitrates!
B. However, an undigestible, or less digestible fish food can cause a problem that the uneducated and ignorant think they need to “solve” with a “filter”. If you are feeding your fish too much, or feeding them a cheap fish food, you will have large undigested chunks of fish food going out into your system and coating your plant roots, instead of getting turned into ammonia, then nitrites, then nitrates. These “large chunks” will still seem super small to you, but are so large, and present so little surface area for the bacteria to go to work on, that they effectively throttle the bacteria’s ability to convert them into something that is easily used by your plants. It’s as if someone glued cheeseburgers all over you, then handcuffed you. The food is theoretically within your reach, you just can’t get to it. Neither can the bacteria or the plants in this type of situation.
We saw this phenomenon at one of our student’s systems here on the Big Island. I just happened to visit his farm, and checked out his plant roots: they were slimy; grey and brown and ugly; and the plants looked unenthusiastic. This was not at all like what I’d seen here on an earlier visit, and I started wondering why at once.Then I went over to the fish tank and checked the texture of the fish poop floating on the surface: it was GRITTY, with many large grains of fish food still undigested in the poop. Since we’d never used an undigestible fish food before on our farm, I’d never seen this condition in an aquaponics system.
But I knew there was a problem somewhere. To figure it out, all I did was compare what was different about his system (which wasn’t working!) with ours (which was!). The one difference that stuck out like a sore thumb was the gritty fish poops. I checked his fish food bin, and the fish food pellets were gritty also when I broke a couple of them in my hand. They didn’t turn into dust, the way our fish food did when I broke the pellets.
Instead of being broken up by the constant movement of the airstone bubbles in the fish tank, then being broken down further into nitrites and nitrates by the bacteria, which LOVE all this surface area, this gritty fish poop simply went out and coated all his plant roots. The bacteria, lacking surface area to colonize, simply couldn’t get to work on the gritty fish poop that came from this cheap fish food. When I talked with him about it, he said he had switched two months ago to a cheap fish food that was available locally; it saved him a 5-hour round trip to the feed supply store that sold the good stuff we used. He’d also noticed the decreasingly poor growth but didn’t know what to make of it.
I made a recommendation, he made the 5-hour trip, and within ten days of switching back to the digestible fish food, his plant roots were clean and white again.
Yes, a “filtration system” may take care of this, because it provides an intermediate location that will catch all the decaying organic material and allow it to decay further before passing out into the troughs. But unless the filtration system is easily cleanable of this accumulating organic material, it may just provide a buffer so that the effect of increasing ammonia and decreasing DO is delayed, but not defeated. This is because the stuff will just build up in there and sooner or later go anaerobic and kill your system productivity.
But just using a more digestible fish food that your fish can fully digest will also “fix” this problem, without having to buy and build and plumb any “filters”. Understanding the aquaponics system is always the answer, not jumping to conclusions based on inadequate data or a poor understanding of the situation.
I disagree.
This sounds a lot like you’re throttling your aquaculture system to suit your hydroculture system, and you’ve neglected the bioculture system entirely.
Wasted food is wasted food, I’ll give you that. There’s no point in feeding the fish more than they can process into usable ammonia.
Adding a biofilter to your system is you giving your bacteria a suitable place to live and thrive. Its not that you “need” or “don’t need” a biofilter, you either accommodate your bioculture, or you treat it like an incidental phenomenon. Having more BSA will allow for faster processing, which means higher output.
I would argue that to maximize production, you need the maximum amount of ammonia you can process from your aquaculture system. This means feeding them as much that is practical. Your bioculture system needs to be capable of handling that maximum, turning it into nitrates. Accommodating bacteria growth and development seems like a no-brainer… Only then are you able to grow the maximum volume of plants your system can handle- anything else is heavily throttled and below production capacity.
Make sense? Or do you disagree? I do concede and agree that cost/benefit comes into play, and the above theory may not be cost effective.
Best Regards.
Hi Kazetsukai,
What your talking about is a very specific set of conditions where your local market will pay a premium for fish (plus the added cost/time/issues of selling live or processed fish legally in your area). Aquaculture isn’t the main objective because its not profitable in most situations. The profit is in the veggies and as such the LD systems are designed to meet that objective. An additional bio-filter is just wasting money, it gives you no benefit in a Friendly style system.
For commercial systems we recommend you do some research and compare fish food, labor, and electricity prices with wholesale fish prices in your location; then make a reasoned business decision in favor of profitability. In Hawaii, with their costs, the equation is: (2 lbs of food X $1/lb) + (3 KwHr X $0.44/KwHr) + (0.11 hour labor X $10/hr) = $4.42 per pound. It costs them $4.42 a pound to raise a fish so they would be losing money on the fish portion of the operation if the goal was to raise and sell fish because the wholesale price of fish is $2.50/pound for their market.
Here is a post talking more about growing lots of fish- http://old.friendlyaquaponics.com/2015/07/31/growing-lots-of-fish/
And another post specifically about High Density Systems- http://old.friendlyaquaponics.com/2015/08/01/hd-systems/
Hope that helps clarify 🙂
Aloha Kazetsukai San
I’ll try to address the points you made in your comment in order:
1. We’re not “throttling” our aquaculture system to benefit our hydroponics.
We are the ONLY people we know of who have operated both the UVI type systems with 1.5 to 2 pounds of fish per square foot of grow bed area (with settling tanks, biofilters, etc), and our single-tank Low Density systems with 0.05 to 0.3 pounds of fish per square foot of grow bed area. As a result, we are the ONLY ones qualified to give this answer (except for one of our early students who also started with the UVI-type systems and got the same results). THESE SYSTEMS BOTH GROW THE SAME AMOUNT OF PLANTS, regardless of nitrate levels, fish loading, or ammonia levels (although I’ll qualify that statement about ammonia in a moment).
The problem with the fish portion of the UVI-type High Density systems is that they lose money on the fish where we live. The cost of raising the fish is simply $2/lb higher than the wholesale price of the fish; and we’re not independently funded the way UVI or any of the other aquaponics universities are; we can’t afford to ignore the real-world driver of profit in business. So we’ve had to develop systems that get the same vegetable growth using 1/5 the amount of fish. The INSTANT things change economically so that we can make a profit on our fish, we go back to using the UVI-type High-Density systems and high fish loading. It’s simply economics, not whether or not we “like” the idea of raising LOTS of fish.
So, regardless of what people say, unless you can come up with a concrete instance of someone who has demonstrated a HIGHER level of vegetable production with a system with a biofilter included (and you’d have to have two identical systems side by side, one with, and one without the biofilter to make that a scientifically supportable conclusion), I’ll have to say that there is no benefit, production-wise, to having a biofilter over not having one.
In addition, I did a thought experiment once, where I “spent” $10,000 to build a biofilter tank; this amount included the cost for the tank, the Kaldnes media, the airstones, the additional blower, and all the hardware. When I compared the area of the media and the tank surfaces added together, I ended up with about 7,000 square feet; a little more than 10% of the root area I had calculated for this system (60,000 square feet of root area). Now my question is, why would I want to spend all that money for a biofilter if I’ve already got plenty of surface area for my surface-colonizing nitrifying bacteria to live one, and I don’t have to pay anything for it?
2. Ah, but you say “I would argue that to maximize production, you need the maximum amount of ammonia you can process from your aquaculture system”. So isn’t more ammonia a good thing? Well, no; actually it isn’t: for one, we already tried that; we started with the UVI-type systems that usually ran at much higher ammonia levels (1-2 ppm instead of the 0.25 to 0.5 ppm our Low Density systems do), and there was no increase in vegetable production, either by weight, number, or shorter growth times. Period.
Second, it doesn’t matter how much ammonia you have in your system if your plants are already getting more than adequate nutrition; it’s like having more food in your refrigerator when you’re already eating well: the extra food in the fridge doesn’t mean you’ll grow more or have a bigger body.
Third, if, because you don’t understand the role of ammonia in your system, you keep feeding your fish more and more, and keep putting more fish into the system until the level of ammonia in your system increases past the level which your nitrifying bacteria can process, it can get so high (typically above 3 ppm) that your nitrifying bacteria begin to shut down and you actually get LESS plant growth rather than more. So no, “more ammonia” isn’t necessarily a good thing, if you understand how these systems work.
Incidentally, our water quality in our Low Density systems is usually < 0.5 ppm ammonia and nitrites, and < 10 ppm nitrates; these are excellent numbers by any aquaculturist's book. In fact, we've had aquaculturists tell us we're lying, or are stupid about taking measurements, when we quote these numbers (tell that to my redheaded wife, with a major in biology and a minor degree in chemistry, if you want to get your head ripped off!). With Warm Aloha, Tim..............
Hi Tim,
I appreciate the effort of putting in your time to create this awesome information. I’m stuck at calculating the BSA of the roots. You mentioned you calculated the roots to have a BSA of 60,000 ft². How did you come up with this number? I can’t seem to find anything that relates to that number online.
Thank you.
Aloha Naomi
There isn’t anything online about the BSA of the roots. The university aquaponics establishment is spending their time on other things. We think the interaction of the bacteria on the roots with the plants and with the ammonia in the system would probably be one of the most profitable things for these folks to investigate, with their labs and research budgets. But no one seems to be aware of the fact that that is where the nitrates that the plants actually use come from: right off the bacterial colonies that grow on the roots themselves.
This is the only thing we’ve come up with to explain the fact that our organic aquaponics systems will grow beautiful vegetables for months at a time with nitrate levels OF ZERO, using a test that’s sensitive to 1 ppm. There’s always 0.25 to .50 ppm ammonia in these systems; that is necessary for the nitrifying bacteria on the plant roots to do their job and feed the plants, but there are no measurable nitrites or nitrates in the water itself. Months at a time.
To calculate the total area of the roots in our system, I took an average-sized lettuce plant from our system and cut about half the roots off it; that was a lot! Then I took a series of root diameter measurements with a micrometer, and measured the root’s lengths with a ruler. Then I counted them, and did some back-of-the-napkin math (simple addition, multiplication, and averaging) to arrive at an approximation of how much root area there is in our 5,000 square foot aquaponics system.
I’m sure someone with a research budget and more time on their hands than a farmer who has to pay the bills every month could come up with a more accurate number.
With Warm Aloha, Tim
Hi Tim, without being a plumber or expert, I am trying to figure out the filtration system in AP and wondered if I could possibly use grow-beds as a filtration system (or part thereof) as part of my clean up process?? The different options and opinions are just overwhelming.
My idea is to do small scale combination of AP (NFT, grow beds and vertical towers) in an area where we have seriously nice water (koi are surviving in a dam outside without being fed), enough space and loads of sun, but go slow on the fish production till I got the systems sorted.
I don’t have an unlimited budget to spend and would like to make as few mistakes as possible. Any suggestions
Hi Gideon,
Simply put, you don’t need a filtration system with the Friendly systems. They cost you more money and give you zero benefit. Use a quality fish food like the Silver Cup or the Rangen 1/8-inch floating catfish food. Don’t feed them too much and you will not have a problem.
There are a lot of opinions out there like you said but Friendly Aquaponic’s prides itself on designing and innovating systems that work great without killing your budget. Tim and Susanne wrote down every single step, material lists, notes and recommendations in the manuals so that you don’t have to waste time, effort and money. I would recommend getting started with a Microsystem; getting used to how that runs, the fish, the produce, the process. Tim always says “start small and build from there” especially when you want to build smart and not waste money and time.
Best of luck with your system!
-Jess
Hi Tim !
That’s interesting to read…
However, which fish food should we use?
Are they some indicators to check about the quality of the food we use?
Cheers,
Mat
Hi Mat,
The post your looking for is here:
https://old.friendlyaquaponics.com/2015/08/26/daily-weekly-and-monthly-tasks-in-a-commercial-aquaponics-system/#more-2040
Have a great day!
-Jess
Mat, we have good luck with both Silver Cup and Rangen 1/8-inch floating catfish food. Sometimes this is called omnivorous fish food.
If you can’t get either of these, try to find something that comes in 1/8-inch pellets, and that when crushed between your fingers, turns into a fine powder instead of a gritty powder. Then you have to run it through the fish and check it after it comes out the exhaust end: is it slimy, with no gritty stuff in it? If so, it’s probably OK.
Aloha, Tim…………
Good read for sure, thanks for educating me. Love it!!! Hope to see more