Sized from the feed#
SLOP4761 · Week 5 · Aquaponics, operating conditions and the law
Where we are#
Week 4 capped how much of the ration you can grow. Week 5 sizes the system that eats it — and finds the constraint no model in this course can see.
Still scoping. Quiz 2 runs at the start of the tutorial, on weeks 4 and 5.
This week’s question#
Aquaponics is sized from the feed — not from the fish, and not from the plants.
Given your climate and the law where your site is: what can you keep, for how many months, and what does that let you grow above it?
By the end you can#
- Size a grow bed and a stocking density from the FAO feed-rate ratio
- Name the operating conditions a running system has to hold
- Find and cite the instrument that governs keeping a species in your client’s jurisdiction
FAO Technical Paper 589#
| Rule | Figure | Where |
|---|---|---|
| Feed rate, leafy greens | 40–50 g/m²/day | p. 17, §2.4.2 |
| Feed rate, fruiting vegetables | 50–80 g/m²/day | p. 17, §2.4.2 |
| Maximum stocking density | 20 kg per 1,000 L | p. 109, §7.3.3 |
| Daily water loss | 1–3 % of system volume | p. 29, §3.4 |
That last line matters more than it looks: a 1 m³ system loses 10–30 L a day. The course carries a 20 L/day placeholder and sizes it properly in weeks 7–9.
Aquaponics is not where your water goes.
Worked example: Adelaide#
Monthly mean 11.3 to 22.7 °C. No single legal species covers that, so Adelaide needs a rotation — harvest and restock, not one continuous stock.
A 4 m² bed at 50 g/m²/day for twelve months:
50 × 4 × 365 = 73 kg feed/year 73 ÷ FCR 2.0 = 36.5 kg live fish × 40 % fillet × 20 % protein = 2.9 kg protein
Apply the closure rule — Adelaide’s larvae cover 9 % of the ration:
2.9 kg × 0.09 = 0.26 kg counted, against 67.5 kg required
The tank is a nutrient delivery system#
that happens to produce a meal. Size it for the greens.
What the model cannot see#
The screening model ranks by temperature alone. For Canberra it returns Murray cod and rainbow trout, seven months.
Murray cod is precisely what an ACT household may not keep without a licence.
The instrument, not the forum post#
The Nature Conservation Act 2014 (ACT) excludes fish from “animal” unless the fish has special protection status. Murray cod is EPBC-listed; silver perch is ACT-vulnerable and EPBC critically endangered.
Importing any live fish into the ACT needs a licence or written approval.
In Queensland, SA and the NT the definitions turn on sale, which is why those answers are shorter. Redclaw crayfish is noxious in South Australia.
Your tutorial task#
- Quiz 2, twenty minutes
- Size bed area, feed rate, stocking, FCR, fillet yield — then check against 20 kg/1,000 L
- Write the operating conditions on sheet 3: temperature band, pH, alkalinity
- Find the instrument. Not a forum post, not a supplier page
Output: a sized fish and bed pair, the approval pathway cited, and protein counted net of imported feed.
Before you leave#
- Is stocking under 20 kg per 1,000 L?
- Does your species row name its temperature band and its source?
- Have you cited an Act, a regulation or a government page?
- Is the protein you carried forward the net figure?
Full citations in the week 5 notes.