There seems to be some ‘confusion’ about feed rates and I believe we’ve mentioned this far more than once in some blog posts and/or comments (both feed inputs and composition definitely covered in publications). Rather than trying to find that or asking you to do so, I’m copying below some more recent responses to feed related questions.
Do note that all this is strictly in regard to Tilapia with a balanced commercial feed (in my case of a known elemental composition). I highly encourage others who are serious about plant production to have their fish feed analyzed (by a qualified lab) for the plant essential elements (yes, it will have a cost, what doesn’t? – except my efforts and time that is ! – to date).
If you have the option, feeds ‘fortified’ with mineral and vitamin supplement ‘packs’ are not necessary. IMO, knowing what the amount of plant nutrients are in a particular feed will be useful information for you to have (and report). If you have your’s tested, report the results to us and I/we will provide feedback.
Note: Anyone growing goldfish or other carps, perch, bluegill etc. should also know (IMO) what their feed composition is and I can offer ZERO suggestions as to what the appropriate feed rates (or temps, DO, etc) are at any size or density for any species except tilapia. Also, if you have some prior experience with gravel or clay-pebble media, you will find being able to feed at a much greater rate when using sand as the filter media.
Response to Questions
RE: report of ‘slow’ plant development with indications of nutrient stress
If I’m understanding you correctly: ‘wastes’ from 80 grams/day distributed over 30 m2 = 2.67 g/m2/day … which is ‘basically nothing’ – aka, no where near enough nutrient to support vigorous plant development
In the ratio studies (all-male Tilapia):
Feed given over the first 31 days starting with N= 80/m3, 15 g fingerlings (includes 1 week at very low rate at start-up before ‘cycled’) = 3.43 kg/m3 (per tank, 31 days)
At v:v 1:2, aka v:a 1:6 = 572 g/m2 (filter) or 18.44 g/m2/day (first 31 day average)
I also looked up the feed input rate data over the first 103 days.
- First week input rate at 4.5% of biomass/day tapering off to 2.1%/day (last week avg.)
- Total feed (mean) per individual = 257 g
- Input rate as % of Pm (day 7)= 9.7%/day
- Input rate as % of Pmf (day 103) = 1.8%/day…BTW: “P” = individual, “m” = mass (weight), “i” – initial, “f” = final
The one-year feed input rate averaged 133 g/m3/day….which at v:a 1:6 = 22.17 g/m2/d.
- 2/3rds of that time was with fish larger than 300g (reduced feed as % of biomass/day and w/ lower FCR than smaller tilapia)…BTW: feed rate %/size and FCR are NOT linear functions
- also included a 40+ day interval without any plants (intentional), then another month trying to raise pH again (with a reduced feed rate)
SO … I ‘feel’ that approx. 150 g/m3/day long-term average is a viable target (perhaps more w/ continuous/vigorous fruiting plant production).
At v:v 1:2, then v:a= 1:6 , so feed rate (‘wastes’ from) per m2 of filter in the 25 to 30 g/day range as a long term average (until determined either excessive/insufficient).
SO, if you can’t get the stocked fish to consume enough feed to sufficiently fertilize the entire biofilter area you have available, then temporarily reduce the portion of filter being irrigated/fertilized until they will eat enough to support more plant growth. This can be accomplished by temporarily blocking off the furrows (length of) to limit the area receiving nutrient and just grow plants (initially) in that section until you are able to feed at a higher rate and increase active filter/plant area.
RE: Another response to similar question
My one-year feed input rate averaged 133 g/m3/day (all-male tilapia)
2/3rds of that time was with fish larger than ~250g (reduced % of biomass/day and w/ lower FCR with increasing size)
also included 40+ days without any plants, then another month trying to raise pH again (reduced feed rate)
SO … I ‘feel’ that approx. 150 g/m3/day long-term average is a viable target (perhaps more w/ continuous/vigorous plant production)
At v:v 1:2, then v:a= 1:6 , so feed rate/m2 of filter in the 25 to 30 g/day range (until determined either excessive/insufficient). During a system start-up )with small fish and young plants) one can feed as much as the fish will eat twice a day and the plants should be okay (was for me) with the feed input increasing as both the fish and plants grow. I believe that my initial feed rate during the first start-up ( still ‘cycling’, microbial populations just starting to develop) was 40 g/m3/day (at v:v 1:2 = 6.7 g/m2/day and was at 120 g/m3/d (20 g/m2/d) or more within a couple weeks.
What is the optimum water:sand ration? 1:2.4 or 1:1.5?
Depends on several factors, but over the long-run, the amount of feed input determines the amount of fish ‘waste’ generated, and the amount of ‘waste’ being accommodated (on average, over time, many months to a year) would dictate the appropriate filter volume. More feed = more ‘waste’ = more filter surface and more soil biology to process.
We have been suggesting v:v =1:2 (or v:a 1:6) for first time adopters as suitable for from 80 to 100 tilapia per cubic meter grown from 15 g to 250+/- gram in 3 to 4 months assuming they are feed a balanced ration fed all they will eat twice a day. Once they’ve attained 250 g (approximately) then the ‘standing biomass’ should be reduced (by culling or increasing volume(s)).
Since I’m mainly interested in the ‘wastes’ (more than the fish production), one could also have greater fish numbers and feed them less intensively (grow more slowly) or even fewer fish and fed very aggressively assuming that water quality remains ‘good’ (allows)
What is the fish density? by weight or by number? assuming 15 grams fingerlings?
In the ratio study. I had N= 80 m-3 at Pmi =15 g – they did ‘fine’ across all the v:v ratios from 1:0.67 to 1:2.25
At v:v 1:2, one should be able to do well at N=100 m-3 (reduce N when attaining 250 +/- 50 g average size).
Growth rate and FCR was slightly better in the higher ratios due to ‘cleaner’ water. Plant yield per plant and per area was better at the lower ratios but total plant yield per filter (not area) and per gram of feed input and per fish growth/increase was greater at the higher ratios. The combined yields per unit feed input was found to be between the 1:1.5 and 1:2.25 ratios (under those prevailing conditions), So, I’ve suggested 1:2 for beginners for both simplicity and leaning toward the larger biofilter capacity to error on the side of caution (for the fish). Also note that this was with (for) indeterminate tomato and cucumber and not for leaf crops, legumes and/or cole (Brassica) family.
There is no magic one-size-fits-all number for feeding rate. All feeds vary in composition, All fish species and growth phases have different requirements (upper and lower limits and an unknowable optimal rate on any given day), All sand, water qualities and locations will be at least somewhat different – overall and as time/seasons progress. All plant species and phases of their growth will have somewhat different nutrient uptake rates (by amount and element – each and every day).
The fish will indicate through their feeding behavior if they are hungry (when full). The plants will ‘tell you’ by their growth rate and any foliar symptoms that might develop if they are getting enough nutrient or not.
As a ‘system’ matures (elements accumulate), feed (nutrient) input each and every day is not critical from the plant’s ‘perspective’.. Longer term (monthly) feed rate, aka ‘waste’ generation should be approximately balanced with the prevailing average plant nutrient uptake. As the ‘soil’ develops, as with an in-ground garden, there is no need to add fertilizers to the media (plants) each and every day (or even week). Sure, the fish will want to be fed every day – but provide enough feed ‘run through’ enough fish to supply the nutrient demands of the plants (number, species) you are growing. Not more (long term), not less (long term). Balance.
There are dozens of variables ‘at play’- every day, changing one aspect/parameter WILL influence everything else eventually, This is the ‘nature’ of an (every) integrated “SYSTEM”. Know what is actual happening in your system (pH, temp, DO, feed input/quality, FCR, etc.) , Observe what is happening carefully and often. Observe, assess, adjust, observe, assess adjust, repeat, repeat repeatedly.
REMINDER: Plant nutrition is STRONGLY influenced by pH. … with 6.4 to 6.5 generally ideal for most species and elements. I suggest the outer limits for good plant nutrition/growth to be pH 5.8 on low (acid) side and 6.8 on the high side. Most AP seem to claim/prefer to exceed pH 7.0. This is NOT ‘good’ (recommended). Facts are facts and unsubstantiated opinions aren’t. Believe it or not. Totally your choice. Every and ALL content I/we provide is exclusively intended to be to your direct benefit. Argument (in the absence of evidence) is not appreciated.
And, as another reminder, iAVs is 90+% about plants. Fish growth is a means to an end. It’s the metabolic ‘waste’ products (and microbial ‘processing’ thereof) from the fish growth (feed) where the value resides (both economic and nutritional). If you are merely interested in fish production and with tinkering with equipment, plumbing and sundry gadgets&gizmos then (IMO) stick to standard recirculatory aquaculture practices (not so-called ‘aquaponics’ – whatever it is you ‘think’ that is/involves). Seriously !
I can’t seem to reply to that comment thread anymore. It appeared to be implied in your last sentence. Apologies if I misinterpreted it.
Thanks for posting this Mark. I was just looking for exactly these numbers. I have read pretty much every post on this site and all of the publications. All I recall finding that addresses this issue was the recommendation of FT:growbed volumes. I think it is helpful to put feedrate front and centre because once you have a guideline on that you can work backwards and calculate everything from there.
Currently my FT volume is double the volume of my beds, 4 times your recommended ratio. But that just means my fish have more room to play, the number that really matters is how much waste they are producing. So my ratio is fine as long as I stock 1/4 of the density.
Damn – had a long detailed reply generated – and also to Aswin (below) – BUT I then got interrupted by an unannounced visit by the County Tax Assessors office and when I returned, my browser had somehow crashed and I lost it all – I have no time or energy to attempt a repeat on a dozen or so ‘points’/aspects. Sorry ’bout that guys – I can’t make my entire day and life responding to iAVs – especially always for free, ntm over and over and over.
The stocking/feed info IS on the site/blog somewhere (and pubs). That it has been overlooked/buried/whatever is unfortunate. We’ve intended to cover this subject – and a dozen-plus others as well – more in depth for a while now (over 50 drafts posts waiting). However, both Gary and I have lives that require our regular attention and also MANY other iAVs related projects/inquiries every day to try to get/stay on top of. In addition to the fact that neither of us has seen a single cent or meaningful/tangible result from any of our efforts ever (in my case since 1984). Yeah, I’m weary, extremely frustrated, depressed and too often angry … apparently unable to keep that from showing through.
BTW, to be blunt, if (IF) you ‘think’ that vermiculture is somehow an adequate substitute for fish metabolites and fish feed (elemental) inputs for viable plant production, then you’re ‘freaking nuts’ aka ‘crazy’. And which would NOT be iAVs – at all. No offense intended – ‘just’ stating reality as I understand it.
None taken. I agree it would not be iAVs and I wouldn’t claim it be. For a start there’s no ‘A’ in it. However use of a dedicated worm bed in place of fish has been trialed successfully before with both gravel growbeds and NFT (The latter was a Central Qld University trial). I would think the suitability of worm outputs would rather depend on what you put into them. Maybe I’ll feed them fishfood and eliminate one variable.
If it displeases you then hopefully it will mitigate that displeasure somewhat to know I will also have a traditional fish powered iAVs system running alongside for comparison built as closely as possible to your spec. In time these side by side comparisons may provide the empirical evidence needed to support the assertion that I’m ‘freaking nuts’. I don’t mind. At least then I’ll know one way or the other 🙂
I am curious to see if a sand growbed would have beneficial effects. I understand that there will be huge differences in the microbial ecology. And some functions of the iAVs bed may not be relevant. Some factors may even be detrimental (i.e. will the worm casting solution form a detritus layer? Or will it clog the sand?) However the massive interface area between microbes and oxygen would have some impact I would imagine. Possibly you know something I don’t that if I did know might give me a reason not to bother trying. But in the absence of that knowledge I can only try it out and see.
Anyway… All jest aside, thankyou for your continuing efforts. If I had the money to pay you or Gary for your advice or to fund Dr Mark’s iAVs research facility I would love to. But my circumstances aren’t that great at the moment. All I can do in the meantime is run a system and report my results. I’ll fill out your spreadsheet once it’s up and running (the fish system I mean, I don’t imagine you’ll want to hear about the worms).
I am NOT a worm ‘expert’ by any stretch, but everything I’ve seen states that worms primarily consume bacteria growing on small pieces of decaying vegetable matter. If this is true, then I see them as directly antagonistic in an iAVs biofilter. This is entirely ignoring where are the plant essential elemental inputs (as biomolecules) being sourced from. ‘Take’ any ingredient of a fish feed – such as corn meal for example – the composition of the corn as going into the digestive tract of a fish is of a given composition and what comes out the back-side of the fish is quite different (different biomolecules/composition). Therefore, the decomposers (microbes) that would break-down undigested corn meal will not be the same organisms ‘breaking-down’ the fish feces from said corn.
If you or anyone else does ‘things’ differently than what was defined/described/proven in iAVs, then it’s not iAVs. Anyone can =and likely will entirely regardless of any/all evidence – do whatever they feel like. But if whatever that might be is not iAVs, then it is NOT iAVs.
And, BTW, try to appreciate that I’ve directly encountered/interacted with perhaps 10,000 people wrt iAVs over the past 30 years. Out of that number I can count on one hand those that actually ‘got it’ – understood (or at least accepted) the processes/biology/ecology engaged – who accepted that what I know/recommend has validity and efficacy (and that I offer the advice that I do for the intended benefit of others and not for my own benefit). Everyone else harbors and defends a personal overt fantasy that they somehow actually know better/different. This is something that I freely admit to being no longer able to be receptive to/tolerant of willful and/or argumentation from ignorance.
Just to clarify, I’m not proposing putting worms in the sandbed. I have some doubts whether they’d like it and I also think they might cause problems.
I think you might be misunderstanding where I’m coming from Mark. I did NOT come across iAVs then decide to try and improve/modify it with worms.
In fact I was planning to build a vermiponic system before I’d ever heard of iAVs. My interest in vermiponics was eliminating some of the downsides and dependencies of using fish as a nutrient source in a growing system. Originally I had planned to trial a floating raft and gravel growbed for the plant side of the system but was looking into alternatives and came across iAVs. It seemed likely to me that a sand bed might provide several benefits over the other systems. Not the same set of benefits it provides in iAVs but probably an intersecting set. There may also be downsides but I won’t know unless I try it. ‘Just do it’ you’re always saying.
So I set about learning all I could. To that effect I’ve read every single post and every single comment on this site, all of the publications (some of them several times) and I’ve searched for and read every single one of your posts/replies on APN. You can call me willfully ignorant if you like but I’ve done everything I can to learn all I can about your method.
Anyways in that process I was so impressed with what I learned that I decided in addition to building my vermiponics systems I would also convert my existing AP system to iAVs, which I’ve already started doing. I’m sure you would have preferred I built an additional system so I could compare the original with iAVs but I have limited space so it wasn’t an option. If you’re bothered by the fact that I’m doing something with sand that’s not iAVs perhaps focus on the fact that I am also concurrently doing iAVs according the doctrine. In fact having an iAVs system will provide one enormous benefit to my vermiponics trials. It will give me a benchmark against which to measure it’s results.
As to the differences in microbial activity I am more than happy to discuss this with you for hours on end because you usually have something to say that I can learn from. But I don’t think you want to so I’ll just leave it there.
I admit to being an intolerant massive dick with full-body first-degree burns but I do not recall specifically referring to you as “willfully ignorant”.
Very use ful post Mark So many are still confused of density of fish and sand…
Mark ,my new system is having 1.5 m3 water and 2.25 m3 sand .i’m planning to stock it with 150 fishes …what is your openion..
Yeah, that’s a v:v ratio of 1:1.5 and should be fine. Assuming Tilapia with feed quality and input rate being similar to what I used, then there should be very adequate ‘waste’ (nutrient) for the plants (suggest vertical fruiting species, not leaf/legumes at this ratio). The fish growth may (might) be a bit slower than with a larger filter but not by much.
We’ve employed the v:v ratio terms (physical sizes) in an attempt to make it simple to grasp in a physical sense but in reality iAVs is a biological system – so ‘actually’ the tank volume aspect includes at a given number of tilapia and at a given feed input rate with the type of feed used. Or alternatively, how many plants can be grown well from a given amount of fish ‘wastes’ (and/or growth). I’d think it fairly obvious that 1 m3 of tank with 1 or 2 fish feed only a few grams of feed/day is certainly not enough nutrient (‘waste’) to grown more than a single lettuce plant. And 500 fingerlings/m3 being feed 1kg/day would produce far too much ‘waste’ to be accommodated by 6 m2 of growing area. So a tank volume includes an approximate amount of fish and cumulative feed input.
The whole ratio ‘thing’ was very useful to determine what fish to plant ratio produced the better results and is relatively simple to understand in a physical sense for people to whom all this is a totally new concept. It may have been a mistake (for some) to describe/explain iAVs in terms of volume ratios – however we have tried to say that this applies at a given amount of fish and feed input (and pH and by fish/plant species). There is nothing ‘magic’ about 1:2 or about iAVs in general. Its biology, iAVs is an intentional ecosystem. In any ecosystem there are very many dependent interactions wherein virtually everything either directly or indirectly influences everything else in the complex/intricate web of life. Given the dozens of variable/influential factors and feedbacks, it’s not an easy thing to describe – especially to those who are not learned (aware) of how an ecosystem cycles nutrient and energy flows – and how the ‘web-of-life’ includes very very many interconnected synergistic (and/or antagonistic) relationships on multiple trophic levels – NTM that microbial activity/processes vastly dominates and 100% facilitates (‘drives’, powers) all multicellular life processes and nutrient flows on Earth.
thank you mark….
This link I got from iAVs fb group.Are you aware of those messages…
Yeah – I saw those interactions – and far more – back when they were occurring (2+/- decades ago). If you are asking for my opinion, Rakocy is a duplicitous lying obnoxious categorical fraud – full stop period. He and I have had an adversarial relationship (at his insistence) since I contacted him in July 1986 and offered to share (provide) my data (to date) and he said, “Fuck you and fuck off and do not contact me again.” It has never gotten any better since. You and others would be shocked to learn what he has (and claimed but hasn’t) done over the years NTM what he is currently ‘up to’ in Bangkok. – I do mean “shocked” as in totally disgusted.
PS – 1986 was way before he did any so-called raft “demonstration” (which never was “researched” in any accepted scientific sense and therefore never could be published in a peer-reviewed journal and weren’t. Self-reporting/self publishing including seminars, books, web posts etc etc are not “published” in a scientific context. Self-reporting is advertising, marketing, promotion – not science.