Backyard Aquaponics
A place to discuss aquaponics

Seems like quite different schools of thought really... Doesn't an ecosystem become more stable the more components are included within it? There's the path of bigger is better, environmental controls, and simple monocultures which can be controlled, being the path to feeding the world. But, I think the complete opposite is true.

Intricate productive ecosystems that utilize waste streams where ever possible, small locally based food production systems that grow a variety of produce seasonally for local people is the best way to grow food as we move into the future.

That sort of thinking doesn't just doesn't fit for most people involved in aquaculture and hydroponic circles.. And that's fair enough, when you have a life time trained in certain methods and you see them work, you stick with what you know.

Good points Joel. I think in time as we learn more from each other and each area, modifications can be made to both our thinking and designs.

Personally, I completely enjoy working on the integrated gardens we get to build from time to time as most of the strict science tends to give way to creative thinking and leaves me with greater flexibility and enjoyment. The production from these systems is no where near that of commercial expectations, but they at least let me have some fun with the designs and construction.

If a growbed can do the filtering and produce a cash crop (or two) without displacing a fish tank it makes sense to do so because I suspect it would cost just as much to do the filtering some other way. In addition you are spreading your risk and improving cash flow by having multiple crops. For the larger setups I could see having a sludge digester to handle solids the growbeds couldn't. Methane could be produced and used for heating.




A valid point regarding the organic fertilizers when you are considering a business although raising fish at low stocking densities could be made a selling point over the long term. You would still either need a distribution system or additional labor to spread the fertilizer. You might also wind up using more water resources depending on how you carry this out. You might as well grow fish with the algae that your excess fertilizer could grow.

Regarding the risk and compromises of running a commercial AP system. We're probably on different wavelengths on this but here goes. You don't have to know everything about what goes on in the system - just what goes in and what comes out. Study over time along with monitoring will help you predict what will happen and correct problems before they occur.

Lets face it, humans have been growing crops in soil for years (and very profitably) yet we know very little about the organisms inhabiting these soils or their interactions and really most of that was learned in the last 100 years or so. A gram of soil is thought to have more organisms than there are humans on the planet Earth. AP really isn't any worse than soil.

Eventually AP will be scaled up because two crops in the same space are more profitable than one and spread your risk out in the event one crop fails (seems inevitable to me). Government will probably have to get the ball rolling to prove scaling it up works (nobody ever wants to be the first ). It won't replace soil farming but I'll bet there is a niche in arid countries where water is expensive and warm countries where it's hard to grow cool season crops. Might also wind up where soil has high heavy metals or salt concentrations.

Thats where I feel some of the issues arise from mindset... While I can't comprehend the mindset of growing food in sterile environments, someone like Paul who has only ever had sterile environments, control and maximizing outputs, can't quite get he idea of lower stocking levels of fish and increased complexity of ecosystem within systems.

Now there's commercial and then there's commercial.. Commercial production does NOT hinge on growing the most physically possible in a given area.

Classic comparison, I went to a great little place out in the country on the weekend where they brew cider, they were a commercially viable brewery supporting a couple of families, they sold through their own premise and online and after chatting to the owner for quite some time I found that they were doing well and expanding things.

Now if you spoke to fosters or millers, or any other multinational breweries they would laugh at the methods they were using to brew their local stuff, but they use plastic barrels and IBCs and they make a beautiful drop.. Are they any less of a commercial venture just because they aren't multinational? Or because they don't use the same methods as the big ones?

Joel,

I'd still rate them as commercial just a different business model (no middle man). They don't have to be the low price leader.



I agree, getting the most physically possible is rarely the most efficient way to do things. They do fertilize and they do double crop. It all depends on the situation and the value of the product vs the cost to produce it in various ways.

Earthan Group



This would be really interesting to test a growbed for the dissolved oxygen drop from inflow to outfall to find out when a bacterial die off was becoming likely. If the DO is low going out, an increase in temperature (and lower oxygen carrying capacity) could cause a die off but you would be forewarned. Don't know if this would work in practice but it might be worth trying.

I thought the point of trying to work out commercial AP system viability is using the simplicity of Aquaponics and upscaling...?
The curiosity in finding out how big a natural AP system could become... and whether this is commercially viable... is having the chance of using the AP model for its beauty, sustainability, and simplicity... not building an Aquaculture or Hydroponic system with a little something 'extra' added...

... and I also noticed that using swirl filters and bio digestors - which are two simple elements that are easily incorporated for stopping solids build-up of waste and creating anaerobic areas - werent considered in the gravel media discussions regarding oxygen depletion? (especially if you are wanting to focus on crops like tomato or capsicum, where media based beds would be ideal, as well as having the added bonus of being nutient pigs compared to lettuce...)
This is definitely not a dig Earthan Group... just an element that hadnt been discussed by you as a potential answer to the problem and a curiosity as to why.

Also, in your discussions regarding 'oxygen limits' of a system... why is this a problem if you could use swirl filters, bio digestors, and then incorporate a DWC element to your system which follows the GBs? Especially as these need to be oxygenated anyway... wouldnt this re-introduce oxygen into the system to make allowances for any losses through anaerobic activity in the GBs?

I agree EB... I think some peoples ideas of 'commercial size' vary widely... to me it means that if you produce enough to sell commercially and can make a viable business out of this at a profit - its commercial... it doesnt necessarily follow that it has to be a multi-million dollar production... although it would be nice if thats how much your making

It would be an interesting test. I would not be too concerned about a bacterial die off but a population explosion of a species that competes with your nitrifiers. The reduction of oxygen will certainly reduce the capacity for nitrification.



I suppose fragmenting of conversations is the bane of discussions on a forum. In this scenario, I think Steward is planning to use the gravel beds as the primary filtration for a large system which includes a low oxygen sensitive fish at high densities. I did ask the question why deal with your solids inline? Which suggests the use of other filtration methods prior to the grow beds but I did not specify what filtration.



While you can add these to take the waste off to a side stream treatment, I doubt you will get enough of the solids out of the line using swirl filters and the remaining solids will become a problem over time at high density. Even at low density feed loads it is just a matter of time.

To give you an example that might suit non-commercial ideas; I have done what you are suggesting in a small system. 50kg of fish fed about 1kg a day, waste water has 100% exchange every 30 minutes through both radial flow and bio filtration, then settle out over 9m2 meters of aerated DWC and air lifted through a 9 m2 x 500mm deep gravel packed grow bed.

Keep in mind the water does not enter the gravel bed directly after filtration and more solids get to settle out over 9 meters before water is lifted to be filtered over 9 meters (4.5m3) of gravel bed and gravity back to the DWC.

After 12 months and quite a few water changes, the solids are still too high and negatively effect the fish growth and oxygen levels to the point I have to run micron filtration to keep the TSS down to acceptable limits. The organic effluent build up is massive and the sulfide levels in the sludge are toxic.

UVI had issues with solids build up and introduced bird netting after their clarifiers to help remove more of the solids and increased their new water exchange rate and that was in aerated DWC alone.

I cannot see how trapping those solids inline (even after swirl/clarifiers etc), in a gravel bed will not cause issues which when they occur the grower will have absolutely no control over them and will find it quite difficult to rectify. If the grower manages to fix it the fish will be long gone.

If you could leave a gap between the gravel at the bottom of the bed where solids can be regularly removed out of them, you may improve the set up. Basically use the gravel beds as a polisher, as you and others suggest but have the capacity to backwash or flush the beds.

This can method of filtration can be improved by upwelling the water through the beds from under the gravel. It is just an upwelling, media packed filter, the type that was discarded commercially many moons ago and is now generally used in aquarium set ups with low feed rates and fish loads.

I have seen it done before in small systems here in AU though I doubt it will transfer to commercial or at least my expectation of commercial facilities. Why, someone would bother with it, I have no idea but I suspect we are in for a new round of self promotion and marketing on this "newly discovered" method.

Earthan Group,

There is useable information regarding cleanout of growbed solids to be found by looking at Trickling Filter "Ponding" and how this is handled. This site gives an excellent overview http://water.me.vccs.edu/courses/ENV149/trickling.htm

Rock size for trickling filter is usually between 2.5 and 4.0 inches to prevent ponding but if ponding occurs there are ways to flush out the bed - these can be found in the common problems section of the website. I think using worms in our system, helps with the buildup of organic matter and reduces the need to flush the growbeds. Using a Roughing Filter or sedimentation basin in front of the growbeds might be another way of dealing with these issues in a small commercial operation. You could probably get by without any of these extras by just a regular maintenance routine where beds are temporarily disconected and flushed then brought back on line.

I agree Scotty, you can add any number of filters and types of filter to the system. Good to keep in mind that everything you add will require x amount of labour to manage. I just built a trickle filter the size of a small house and have some knowledge around them. One thing is for sure they do not work well with solids. It is important to distinguish the trickle filter discussed in that link is for an aquarium and they also suggest it must be preceded by some sort of solids filter.

I am sure any combination of worms, filters, shrimp and what not will work just fine. My point is you will have to compromise somewhere and it will end up being your stocking density of the fish. If this is not a concern in a commercial set up the size you have in mind, problem solved.

Hey EG, what exactly are you arguing for? I know you said that you should max out the fish operation as much as possible to have enough revenue to be a going concern, and you've talked about how solids etc. can use up all oxygen in the system until all the fish die, but these are the same problems in pure aquaculture, so how is doing a pure aquaculture setup any easier than the same problems you will have in an AP system? Is your point to de couple the fish and plants? So all the excess solids that are so bad on the fish side are just run to waste? Do you suggest running them through more digestion then to the plant loop? So the idea is to not do a recirculating system, in total, only specifically on the fish side and on the plant side as separate loops?

Hi Dave. I am not arguing at all, merely expressing my opinion from my experience with commercial aquaculture and recirc. technology and more recently commercial hydroponics.



That is a good point Dave. We don't have the issues in as you suggest aquaculture because the systems are designed not to have them. Though, if the aquaponic systems are not designed in a similar manner as aquaculture, aquaponics will have all of the same issues you just mentioned.

If you now want to do aquaponics but do not want to employ proven methods used in aquaculture, don't you think aquaponics will be more difficult? Won't aquaponics have more risk simply because you do not want to employ aquaculture techniques and technology to do aquaculture at a commercial level successfully?



No that would defeat the purpose of integrated systems and utilizing the waste from fish farms. Isn't that what we are talking about?.



Simply put yes Dave. You are still using recirc. know how, just a little more measurable and controllable in comparison to the methods I have seen suggested to date. 100% waste reuse, is not that complicated if you have manageable systems.

Do you see any issues with that? Happy to hear them mate.

Actually the trickling filter was for wastewater treatment plants - they have a rotating boom which deposits wastewater onto rocks for processing by organisms fixed on the media. Yes, trickling filters are normally a secondary treatment system and are preceded by some form of solids removal. They are in some ways similar to growbeds, which is why they have some value in this discussion. Growbeds are not as deep and typically don't need aeration from the bottom.



If I were to take an recirculating aquaculture business and add plant production, would you think this was a compromise? I've added plants, I haven't reduced the fish loads, I've added an income stream that wasn't there before and I've reduced my economic risk of crop failure. I've added the cost of the piping and growbeds and any labor required to harvest, process, deliver and market the plants. I may have actually reduced heating costs for the fish if the plants are grown in a greenhouse (relatively cheap structures).

My point is this aquaculture business would need to have a full compliment of wastewater treatment facilities or they wouldn't be allowed to discharge water into a river because it would eat up all the oxygen and kill all the fish in the river (for the same reason you wouldn't recirculate the water back into the RAC fish tank without first treating it). Running it as an aquaponics setup I could grow as many fish as I wanted to AND I could grow as many plants as the fish could support provided I had the room for it and really wanted to. As far as the fish are concerned you'd have all the same problems that you'd normally have in RAC.

EG it just sounds like you're comparing a correctly filtered aquaculture setup with an under filtered AP setup again and again. There are few to no gravel bed systems to use as examples at the sizes you keep mentioning, does that mean they wouldn't work? I can claim a certain system will work without having actually built one, but to me it's the same to say a certain system will not work, when an example has not been built. Someone should try it so we can know, yes?

I am not saying media beds will not work. Simply providing some insights to the issues that will need addressing in water quality and management. Not really sure how many ways I can say that but that is the gist of where I am coming from. If you want to build a commercial media bed facility with or without filtration, it really makes little difference to me. I have offered quite a few suggestion on how they might be managed in a number of threads. If you dissagree, no problem here the advice is free.