This topic would be several long chapters in a book, or an entire book in itself, which I am NOT writing – ever. It is therefore strongly suggested that one study the requirements, behaviours and life-cycle factors of the species you are attempting to grow from responsible sources.
Far TOO many variables to even begin to suggest a ‘standard’ or ‘baseline’.
FACTORS wrt stocked density (collective biomass per unit volume, not the number of individuals)
- Species cultured
- Temperature
- DO level (diurnal low)
- pH, EC, etc.
- Targeted harvest size
- (daily ration rate as % of body weight declines and FCR increases with increasing individual size attained in most if not all species, sometimes dramatically, regardless of other parameters)
- Static vs dynamic stocking management
- Feed Composition
- Feed Ration (rate) and diurnal regime
- Amount of biofiter volume
- Crop(s) and mean current growth (uptake) rate(s)
Factors wrt feed
- Species cultured
- Mean individual size (age) – assuming similar cohorts
- Feed Quality (including elemental composition)
- prevailing water quality factors
- Daily feed regiment
SO FAR
When we add fish feed to the iAVs, we’re actually feeding the entire so-called ‘system’ … the fish, plants and the beneficial micro-organisms that inhabit a mature stable ecosystem.
Mark…..I need anything useful/relevant that you can remember about the feed.
Both P’86 and Ratio Studies used Purina Mills 5140 floating pelletized Catfish Chow, labeled as 32% protein without the ‘normal’ addition of mineral and vitamin supplements. – apparently no longer made/sold (at the time there was no such thing as a tilapia chow in the US and I know less than nothing about what may have been developed since). I do not have an ingredient list.
(click image to enlarge)
Residual levels (plant tissue and media accumulation) of Sulphur, Copper and Zinc were determined to be high, no toxicity symptoms were observed. Obviously, the fish didn’t need/use these in the proportions provided. Potassium began moderately limited (plant tissue) at the highest ratio (largest filter volume). Boron was relatively low for one particular tomato variety grown in the higher (1:1.5 and 1:2.25) ratios.
NOTES on Feed Rates in iAVs Ratio Study: Mean feed ration per day in the iAVs ratio studies (over 370 days) was 133 grams/cubic meter/day. Range was 80 to 360 g/m3/d. Inputs were held constant across all v:v ratios. At a v:v ratio of 1:2 a slightly greater feed rate is possible. These studies were conducted with ‘male’ hybrid tilapia. Young fish consume a higher amount of feed relative to their body weight than do older/larger fish. Mean daily feed rate as % Pmi (individual weight) was 9% @ 15 gram size, 2% @ 250 g, 1% at 500 g, 0.6% at 750 gram. Initial stocking was approx. 80 ea. @ 15 gram fish per cubic meter. They reached Pmi of 265 grams in approx. 115 days. At which point, the number of stocked individuals per tank was reduced (sequentially harvesting larger specimens at approx. 3 month intervals). FCR declines with increasing Pmi in most if not all species. Tilapia are especially noted for this tendency above Pmi of 250 g. Initial FCR was 1:1.1. At 265 g, FCR was 1: 1.5. At 500 g, FCR was approx. 1:2.0. At 750 g, FCR >1:2.5. I was likely overfeeding albeit all feed was being consumed within 5± minutes. The aforementioned 360 g/m3/d feed input rate was not sustainable (advisable) at the biofilter v:v ratios used. BTW, these fish were severely stressed by being sedated every 30 days in order to monitor biomass increase rates. Even though declining growth rates and feed conversion is typical for tilapia, an unknown portion of the documented declines may be attributed to this repeated stress.
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Obligatory rant: Never ‘just’ take anyone’s word or pronouncements as being valid because of their alleged relative ‘expertise’ without also confirming/checking other responsible sources of information. Especially do not blindly accept input from someone who hasn’t actually raised your species at the density, size and with method (feed, filter(s), etc.) that you are employing. And ‘just’ because someone may be charging a fee for dispensing ‘sage’ advice in NO way implies that the content (esp. in your context) will be in anyway accurate/reasoned/sound. There are many thousands of self-inflated know-it-all blowhards ‘out there’ attempting/competing to ‘suck you in’ to their baseless fantasy delusions. Caveat emptor.
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