Gary's mythconceptions #4 - question on solid wastes

[Crusty]

Thanks for the kind words mate.

ie. they prefer to produce a higher ratio of plants to fish. In this situation it would make sense to isolate the solids from the plants and fish, but not entirely remove them from the production loop until they had leached most of their nutrients.

mmm regardless of your plant production requirements, dealing with your solids outside of the production loop will in turn give you more control of the nutrient levels. Treating the solids within a grow bed becomes somewhat problematic over time. Though most of the time, those problems are not easy to see.

Something to keep in mind about solids are the bacteria that break them down, heterotrophs. These are a very dominant, aggressive species of bacteria that gain their energy from that of other organics (our nitrifying bacteria is food to them). They double their population in 20 mins, live in anerobic (no oxygen) and aerobic (oxygen) environments and will produce very high levels of ammonia as a result of their munching. Because of their population capacities they will literally suck the oxygen out of any size system that is rich in organic waste with in an hour (feed input = up to 30% orgainc waste poop and wasted feed by weight).

Because of the oxygen demands placed on every other organism by the organic load, they are best moved out. Deal with them elsewhere and bring the nutrient (ammonia) back in through your biofilter for processing to nitrate. Ever wondered about those sudden deaths we see all the time, with all the water quality parameters readings, nitrogen etc are great?...

There is nothing different about aquaponics. Aquaculture is the management of fish waste and aquaponics is the management of fish waste. There is no reason why the methods of management need be different. The addition of plants is simply and extra step. Stripping out the nitrate and reducing salts build up, there by reducing the amount of water required to be exchanged.

Although this statement is correct I don't think its quite the whole story. If people are only growing for their own needs then there maybe a situation where they actually need nutrients more than they need more fish ie. they prefer to produce a higher ratio of plants to fish. In this situation it would make sense to isolate the solids from the plants and fish, but not entirely remove them from the production loop until they had leached most of their nutrients. Of course in a commercial situation where any extra produce is extra cash, that makes no sense at all.

I agree there is an attainable "balance" that can be achieved from a fish nutrient output to a plant nutrient uptake (resulting in production output of plant volume). Wilson Lenard speaks of this often and practices this in his commercial designs. The major flaw in the backyard environment is that not too many will be achieving this balance without a great deal of trial and error. Don't get me wrong, I think everyone is doing a champion job of designing and building their own units! But at what cost?

Just they same, it takes more of a "suck it an see" approach. EG: If you have too much nutrient, reduce the amount of fish or add more grow beds and so on. This is pretty much the same process used for premade kits, which I would expect more knowledge. The difficulty I have with this approach, is more times than not the "see" part usually ends up with the fish taking the "suck it" part and dieing or living in sub optimal conditions. Rather than starting out with the right, or close to balance to start with. Filtration lets you do this with accuracy and contrary to some beliefs, inexpensive and efficiently.

Consider that 60% of all aquarium fish sold in Australia each year die within the first two weeks of purchase (not sure how they know this or who they are). That is an impressive number of avoidable fish kills. Is the backyard aquaculture (aquaponics) any different?...

[GaryD]

Hi,

First off, I think your doing a great job re-teaching some aquaculture lessons here. I pretty much agree with everything you've posted and you seem to be going about it in a way that is actually gaining some traction. Not just spinning the wheels like my ill-considered attempts.

I agree......it's useful, at last, to have some support in overcoming some of the ill-founded beliefs that attach to aquaponics.

But don't let Gary convince you to dumb down your posts too much, I'm sure not every backyard aquaponicist is afraid of a bit of mathematics.

Someone once wrote, when describing ability, that above the level of genius is what they described as "simple." These were people who could not only comprehend matters that were above the grasp of their contemporaries and who could look at things and see patterns and new paradigms where others could not. Most importantly, they were able to translate life's complexities into words that could be understood by laypersons.

Dumbing down is not what I'm about......but I do know the backyard food production market quite well.

Let's remember that most aquaponicists have two years or less of experience......and they were probably lured to the discipline by suggestions that it was easy to do. Overturning some of the simplistic notions is going to take some time and effort.

Welcome to the journey.

Although this statement is correct I don't think its quite the whole story. If people are only growing for their own needs then there maybe a situation where they actually need nutrients more than they need more fish ie. they prefer to produce a higher ratio of plants to fish. In this situation it would make sense to isolate the solids from the plants and fish, but not entirely remove them from the production loop until they had leached most of their nutrients.

In my view, regardless of the fish/plant focus, the solids should be removed and treated separate to the AP system water column.

I've always advocated solids removal but I'm increasingly of the view that the only successful way to run an AP system is to see it as a discrete recirculating aquaculture system to which a growing system is attached.......rather than seeing the growing system as part of the recirculating aquaculture system.

I suggest this because, sooner or later, you may need to disconnect the aquaculture system from the plant growing unit even it it's just to minimise overnight heat loss.

The other major benefit in this approach is that, if the aquaculture side of the system is self-sufficient, any additional nitrification and aeration afforded by flood and drain grow beds is a bonus rather than essential to the operation of the system. Complete solids removal also means that whatever contribution that the grow beds make is optimised for the fact that they are not full of muck.

Separating the fish completely from the solids is something that should happen for lots of reasons and processing the solids in the same overall water column as the fish simply ignores most of them.

Of the systems that treat solids within the same water column as the fish, the UVI model is arguably the most prominent. The thing that people invariably overlook when referring to this is that this system grows tilapia. They are an exceptionally tough fish which is able to survive (indeed prosper) in conditions that would kill most Australian native species.

Much of the folklore that currently attends aquaponics derives from the fact that the Speraneo model was also premised on tilapia. I think it can be successfully argued that, while it serves as an important milestone in the development of aquaponics, Tom Speraneo might not have had the same success with his system had it been growing Murray cod or barramundi.

Gary

[arachdog]

I certainly wasn't suggesting no filtration. I was just saying that if I had to pick a potential difference in the filtration management of aquaponics and aquaculture, it would be that with aquaculture the faster you get the waste out of the loop the better, end of story. With aquaponics I think it might occasionally be in the interests of a backyard farmer to have a slighter longer retention time.
Admittedly it's quite a narrow range of circumstances though:
Firstly its lightly stocked to start with, so you already have plenty of DO overhead
Secondly the farmer doesn't want to produce more fish, but he does want more vegetables.

I agree Gary that externally processing would be safer, but it also requires more labor. If a system is lightly stocked, well managed, and operating miles within its safe operating zone then I can see a situation where a farmer might perfectly rationally make the decision to only backwash his filter only every second day, for example.

Edit: Obviously the removal of waste has to be balanced with the amount of water it takes to backwash the filter. I thought I better mention that since I'm sure you would have picked it crusty.

[Crusty]

If a system is lightly stocked, well managed, and operating miles within its safe operating zone then I can see a situation where a farmer might perfectly rationally make the decision to only backwash his filter only every second day, for example.

I certainly agree with this line of thinking. I am more about, how the hell the farmer knows he is operating miles within its save operating zone? This part is a complete mystery to me...

[arachdog]

I certainly agree with this line of thinking. I am more about, how the hell the farmer knows he is operating miles within its save operating zone? This part is a complete mystery to me...

Yeah I agree that's a big problem. That's why I think the formulas (we still need some for DO btw ) you've been posting are so important, so people can properly estimate the loads their system will face. Some may find the maths too complicated, but outside continuous water quality monitoring, which is probably doesn't fit into the typical backyarder budget, its the only way to manage the risk.

[Crusty]

Yeah I agree that's a big problem. That's why I think the formulas (we still need some for DO btw ) you've been posting are so important, so people can properly estimate the loads their system will face. Some may find the maths too complicated, but outside continuous water quality monitoring, which is probably doesn't fit into the typical backyarder budget, its the only way to manage the risk.

Dissolved oxygen (DO) formulas are a great deal more complicated ... But I do have them, just have to work out how to clarify them a little bit.

[GaryD]

Hi Arachdog,

I certainly wasn't suggesting no filtration. I was just saying that if I had to pick a potential difference in the filtration management of aquaponics and aquaculture, it would be that with aquaculture the faster you get the waste out of the loop the better, end of story. With aquaponics I think it might occasionally be in the interests of a backyard farmer to have a slighter longer retention time.
Admittedly it's quite a narrow range of circumstances though:
Firstly its lightly stocked to start with, so you already have plenty of DO overhead
Secondly the farmer doesn't want to produce more fish, but he does want more vegetables.

I can see where you're coming from, and if low DO was the only issue, boosting aeration would probably provide a solution. As you are aware, however, there are other compelling reasons to remove solids.....see here.

Let's remember that we don't have to discard the minerals that are bound up in the solids. They can be digested aerobically and the nutrient-rich liquor returned to the system.......without the sludge.

I certainly agree with this line of thinking. I am more about, how the hell the farmer knows he is operating miles within its save operating zone? This part is a complete mystery to me...

The simple answer is that they don't.

Since most backyard farmers will not have invested in equipment to measure DO, they generally won't know that DO is an issue until fish start dying.......and they certainly won't know about autotroph activity or the effect of harmful organisms that are the by-product of the failure to remove solids in a timely fashion.

I'm increasingly of the view that there is really no safe way to run an aquaponics system if it is not thought of as an aquaculture system (with all that implies) first and a plant growing system next. The possible exception might be those systems that grow tilapia. It's interesting (but no big secret in my mind) that the most widely touted success stories in aquaponics (UVI and Speraneo) both ran tilapia.

Gary