Nana Bambi's Place · Ragay, Camarines Sur, Bicol, Philippines
iAVs Technical Operations Reference · Companion to the Pugod Integrated Aquaponic System document
1. Grow Bed Media — Complete Specification
Sand Specification
The sand used in iAVs grow beds is the single most critical material decision. Get this wrong and the entire system fails. The specification is non-negotiable.
| Parameter | Specification |
|---|
| Grain size | 0.4 – 1.2 mm |
| Mineral type | Crystalline quartz or volcanic basaltic |
| Carbonate content | Zero — no limestone, no coral, no shell |
| Clay / silt content | Zero — must drain freely, no fine particles |
| Grain shape | Angular grains preferred (better root grip and capillary action) |
Volcanic Sand — Legazpi / Mayon Source Assessment
Volcanic basaltic sand from the Legazpi / Mayon area is potentially an excellent local source. It offers several advantages:
- Naturally angular grain shape — ideal for root anchorage and capillary wicking
- High mineral content (iron, magnesium, calcium silicates) — beneficial micronutrient release
- Zero carbonate — volcanic basalt does not contain calcium carbonate
- Locally available in Bicol — reduced transport cost vs commercial silica sand
- Grain size typically in the correct range (lahar deposits often 0.4–1.5mm)
FLAG: Heavy metals test required. Volcanic sand from active/recent volcanic zones can contain elevated levels of heavy metals (arsenic, cadmium, lead, mercury). Before committing to Mayon-sourced sand, send a sample to a laboratory for heavy metals analysis. This is a one-time test. If it passes, the source is excellent.
Fallback Source: Commercial Silica Sand
Vital Resource Enterprise — silica sand supplier
Contact: 0917-504-2406
Order crystalline quartz silica sand, 0.4–1.2mm grade. Confirm zero carbonate, zero clay/silt content before purchase.
Three Field Tests
FIELD TESTS — Do all three before committing to any sand source. These are simple, require no lab equipment, and take less than 10 minutes.
| Test | Method | Pass Criteria |
|---|
| 1. Vinegar test (carbonate detection) |
Place a handful of sand in a bowl. Pour household vinegar (any brand) over it. Watch and listen. |
No fizz, no bubbles, no reaction. Any fizzing = carbonate present = reject this sand. |
| 2. Jar turbidity test (clay/silt detection) |
Fill a clear jar or bottle half with sand, add water to top, shake vigorously for 30 seconds, set down and observe. |
Water clears within 60 seconds. If cloudy water persists, fine particles (clay/silt) are present = reject. |
| 3. Bucket percolation test (drainage rate) |
Fill a bucket with sand to 300mm depth. Drill 6mm holes in the base. Flood with water and time how long it takes to drain completely from the surface. |
Surface water drains within 2 minutes. If water pools on top for longer, the sand is too fine or contains clay = reject. |
Media Bill of Materials — Per IBC Half-Tank Grow Bed
Each grow bed is built from a standard 1000L IBC tank cut in half (giving a bed approximately 1200mm L x 1000mm W x 400mm deep).
| Item | Quantity | Notes |
|---|
| Sand (0.4–1.2mm, tested and passed) | ~480 litres | Fills bed to 400mm depth |
| River gravel (20–40mm) | ~25 litres | Base layer over drain holes, prevents sand washout |
| Shade cloth (woven, not knitted) | 1 piece cut to bed floor size | Laid between gravel and sand layers to prevent sand migration |
| Taro pond inoculant water | 20–40 litres | Initial biological inoculation from established taro pond |
IBC Bed Setup Sequence — 10 Steps
- Drill drain holes — 6 x 12mm holes in the base of the IBC half-tank, evenly spaced
- Position drain tray — bed sits on a sloped tray or channel that collects drainage and returns it to the pond
- Lay gravel base — spread 25L river gravel (20–40mm) evenly across the floor, ~25mm deep
- Lay shade cloth — cut to size, lay flat over gravel layer
- Fill with sand — add tested sand to 400mm depth
- Shape ridges and furrows — form 3–4 lengthwise ridges for planting, furrows between for water distribution
- Connect manifold — attach irrigation manifold from pond pump delivery line
- Flood test — run water through, confirm even distribution and complete drainage within 2 minutes
- Inoculate — add 20–40L of taro pond water to introduce beneficial bacteria
- First crops — plant fast-growing leafy greens (pechay, kangkong) within 1–2 weeks of inoculation
INOCULATION ADVANTAGE
The taro pond on the Pugod site is an established, biologically active water body. Using this water to inoculate new sand beds introduces a full complement of nitrifying bacteria (Nitrosomonas, Nitrobacter) from day one. This
reduces the cycling period from the standard 9–12 weeks down to approximately 4–6 weeks. This is a significant operational advantage that most new aquaponic systems do not have.
2. Pond Stocking — Tilapia & System Ratios
Fundamental Ratio
NON-NEGOTIABLE RATIO
1 : 2 — fish tank volume to sand bed volume.
For every 1 litre of fish tank water, you need 2 litres of sand bed volume. This is the foundational McMurtry iAVs ratio. Do not deviate.
Pugod System at Full Scale
| Component | Volume / Count |
|---|
| Pond (fish tank) | 5,000 litres |
| Total sand bed volume required (1:2 ratio) | 10,000 litres |
| IBC half-tank bed volume (each) | ~480 litres |
| Number of IBC beds at full load | 21 beds |
Staged Stocking Approach
STAGED LOGIC: Never stock the full fish load on day one. Build up gradually so the biological filter (sand beds) can keep pace with the ammonia load.
| Stage | Fish Count | Timing | Conditions to Advance |
|---|
| Stage 1 | 150 – 200 fingerlings | System commission | Ammonia stays below 0.5 mg/L for 2 consecutive weeks |
| Stage 2 | Add 150 – 200 fingerlings | 4–6 weeks after Stage 1 | Ammonia stays below 0.5 mg/L for 2 consecutive weeks |
| Stage 3 | Full load: 400 – 500 total | 4–6 weeks after Stage 2 | System fully cycled, all beds planted |
Fish Species and Stock
| Parameter | Specification |
|---|
| Species | Nile tilapia (Oreochromis niloticus) |
| Sex | All-male stock preferred (faster growth, no breeding management) |
| Fingerling size at stocking | 5 – 10 cm |
| Source | BFAR-accredited hatchery or established local supplier |
Feed Rates
- Starting rate: 3% of total fish biomass per day, split into 2–3 feedings
- Near harvest: reduce to 1% of biomass per day
- Adjust based on water temperature and feeding response (fish should consume all feed within 10 minutes)
Feed Conversion (McMurtry Research)
1 kg of feed produces:
• 0.76 kg fish
• 1.66 kg vegetables
This is the validated McMurtry research conversion ratio for iAVs systems. It demonstrates why iAVs is economically superior to fish-only aquaculture — the vegetable output alone exceeds the fish output.
Monitoring Trigger
Ammonia above 0.5 mg/L = action required. Stop feeding for 24 hours. Test again. If still elevated, reduce daily feed by 50% until levels drop. Check all beds are draining properly. Do not add more fish until ammonia is consistently below 0.5 mg/L for two consecutive weeks.
3. Water Management — Valve Controls and Emergency Protocols
Three-Way Valve
The system uses a three-way valve at the water intake point with two positions:
| Position | Water Source | Use Case |
|---|
| NORMAL | Pond water (fish effluent) | Standard daily operation — nutrient-rich water irrigates grow beds |
| FLUSH | River water (clean) | Emergency dilution, monsoon bypass, pre-startup conditioning |
Operational Scenarios
| Scenario | Valve Position | Action | Duration |
|---|
| Normal operation | NORMAL | Pond water cycles through beds on timer/schedule | Continuous |
| Ammonia spike | FLUSH | Dilute pond with river water; stop feeding; run beds on river water until levels drop | 24–72 hours |
| Monsoon / heavy rain | FLUSH | Bypass pond completely; open all bed drain lines permanently; staged overflow management | Duration of storm |
| Pre-startup conditioning | FLUSH | Flush new sand beds with clean river water before introducing fish effluent | 48–72 hours |
VALVE LABELLING: Both valve positions must be permanently labelled in two languages:
• NORMAL (green label) — "Pond Water / Tubig ng Pond"
• FLUSH (red label) — "River Water / Tubig ng Ilog"
Labels must be weatherproof and visible from 2 metres.
Monsoon Bed Drain Protocol
During monsoon or extended heavy rainfall:
- Switch valve to FLUSH position immediately
- Open all drain lines permanently — do not allow water to pool in beds
- Staged overflow: if water volume exceeds drain capacity, allow controlled overflow from beds back to river via overflow channels
- Monitor pond level — if rising, open pond overflow valve to prevent flooding
- Do not feed fish during severe weather events
- After storm passes, wait 4–6 hours, test water, then switch back to NORMAL
FAST WATER IS DANGEROUS — SLOW WATER IS SAFE.
The iAVs system is designed for slow, controlled water movement. Rapid flow erodes sand beds, washes out beneficial bacteria, stresses fish, and destroys root systems. During any emergency scenario, the first priority is to slow the water down, not to increase flow. If in doubt, reduce flow rate and open drains.
Water Quality Monitoring Schedule
| Parameter | Test Frequency | Target Range | Action Trigger |
|---|
| Ammonia (NH3/NH4+) | Daily (first 8 weeks), then 2x/week | < 0.5 mg/L | > 0.5 mg/L: stop feeding, check drains |
| Nitrite (NO2-) | 2x/week (first 8 weeks), then weekly | < 1.0 mg/L | > 1.0 mg/L: partial water change with river water |
| Nitrate (NO3-) | Weekly | 5 – 150 mg/L | > 150 mg/L: increase planting density |
| pH | Weekly | 6.5 – 7.5 | < 6.0 or > 8.0: investigate cause |
| Dissolved oxygen | Daily (visual: fish gasping at surface) | > 5 mg/L | Fish at surface: increase aeration immediately |
| Temperature | Daily | 25 – 32°C | < 20°C: reduce feeding; > 34°C: shade pond, increase aeration |
| Drain clarity | Every flood cycle (visual) | Clear within 30 seconds of drain start | Cloudy drain: check for clogged sand, silt infiltration |
Testing Equipment
A basic aquaponics water test kit is sufficient for all routine monitoring. Source from a Naga aquarium supplier. The kit should include test strips or liquid reagents for ammonia, nitrite, nitrate, and pH. Dissolved oxygen can be monitored visually (fish behaviour) in the early stages; a DO meter can be added later if budget allows.
4. Grow Bed Crop Selection and Management
What iAVs Grows That Raft Cannot
THE CRITICAL COMMERCIAL ADVANTAGE
Raft aquaponics (deep water culture, NFT) can only grow leafy greens and some herbs. iAVs grows
root vegetables — camote, carrots, radish, beetroot, ginger, turmeric — because the plants root into sand, not water. This is the single biggest commercial differentiator. No other aquaponic method can do this.
Crop Categories
Leafy Greens and Herbs
| Crop | Days to Harvest | Notes |
|---|
| Pechay (bok choy) | 25 – 35 | Fast, reliable, high local demand |
| Mustard greens | 30 – 40 | Hardy, pest resistant |
| Lettuce | 30 – 45 | Multiple varieties, continuous harvest |
| Basil | 30 – 40 | Cut-and-come-again; high value per kg |
| Coriander (cilantro) | 25 – 35 | Bolts fast in heat; succession plant |
| Vietnamese mint | Perennial | Once established, continuous harvest |
| Kangkong (water spinach) | 21 – 30 | Extremely fast; cut-and-come-again; thrives in warm wet conditions |
| Watercress | Perennial | Grows in furrows where water collects |
| Lemongrass | 90+ | Perennial once established; harvest outer stalks |
Fruiting Crops
| Crop | Days to Harvest | Notes |
|---|
| Tomatoes | 60 – 90 | Needs staking; high nutrient demand; high value |
| Capsicum (bell pepper) | 70 – 90 | Slower but premium price |
| Eggplant | 60 – 80 | Strong local demand; multiple harvests per plant |
| Cucumber | 45 – 60 | Needs trellis; high water uptake |
| Bitter melon (ampalaya) | 50 – 70 | Grows on trellis; very strong local demand |
| Sitaw (string beans) | 45 – 60 | Climbing; needs support structure |
| Okra | 50 – 65 | Heat tolerant; continuous harvest |
Root Vegetables (iAVs Exclusive)
| Crop | Days to Harvest | Notes |
|---|
| Camote (sweet potato) | 90 – 120 | Tops edible as leafy green during growth; tubers at harvest |
| Carrots | 70 – 90 | Needs deep sand (full 400mm); loose sand = straight roots |
| Radish | 25 – 35 | Very fast; excellent succession crop |
| Beetroot | 55 – 70 | Leaves also edible; dual harvest |
| Ginger | 120 – 150 | High value; partial shade; slow but worth it |
| Turmeric | 120 – 150 | Similar to ginger; shade tolerant; medicinal value |
Planting Strategy
- 50/50 split: aim for approximately 50% fruiting crops and 50% leafy greens across all beds
- Stagger planting dates: do not plant all beds on the same day — stagger by 1–2 weeks to ensure continuous harvest rather than feast-and-famine cycles
- Root vegetables: dedicate specific beds rather than mixing with leafy crops (different harvest timing)
First 5 Beds — Proof-of-Concept Sequence
START WITH FAST CROPS. The first beds must produce visible results within 3–4 weeks to build confidence and prove the system works. Do not start with slow-growing crops.
| Bed | Crop | Rationale | Expected First Harvest |
|---|
| Bed 1 | Pechay | Fastest crop; visible results in 3 weeks; high local demand | Week 3–4 |
| Bed 2 | Kangkong | Almost as fast as pechay; cut-and-come-again means continuous harvest | Week 3–4 |
| Bed 3 | Herbs (basil + coriander) | High value per kg; demonstrates variety; cafe/kitchen use | Week 4–5 |
| Bed 4 | Tomatoes | First fruiting crop trial; needs staking; tests nutrient delivery | Week 8–10 |
| Bed 5 | Carrot trial | Root crop proof-of-concept — the iAVs differentiator; demonstrates what raft cannot do | Week 10–12 |
5. System Startup Checklist — Sequence to First Harvest
This is the complete implementation timeline from pre-build through to first harvest and DA site visit. Every step must be completed in order. Do not skip steps.
| Phase | Step | Task | Duration / Timing |
|---|
| Pre-Build | 1 | River baseline water test — test river water quality before any construction. This is the benchmark against which the system's water quality improvement will be measured. | 1 day |
| 2 | Sand source testing — collect samples from candidate sources (volcanic / commercial). Run all 3 field tests (vinegar, jar turbidity, bucket percolation). Send best candidate for heavy metals lab test if volcanic. | 1–2 weeks |
| 3 | Build drain tray / return channel — construct the sloped drainage infrastructure that returns water from beds to pond. Must be in place before beds are positioned. | 1–2 weeks |
| Build | 4 | IBC bed setup — cut IBCs, drill drain holes, position on drain trays. Start with 5 beds for proof-of-concept. | 2–3 days |
| 5 | Sand fill — gravel base, shade cloth, sand to 400mm. Follow 10-step setup sequence. | 1–2 days per 5 beds |
| 6 | Shape ridges and furrows — form planting ridges in each bed. | Same day as sand fill |
| 7 | Connect manifold and flood test — attach irrigation lines; run water through all beds; confirm even distribution and drainage within 2 minutes. | 1 day |
| Biological Start | 8 | Inoculation — add 20–40L taro pond water to each bed. Begin pre-plant cycling (run clean river water through beds on timer for 48–72 hours to establish bacterial colonies). | 3 days |
| 9 | Commission pond — fill pond, establish aeration, run water loop through beds for 1–2 weeks without fish to stabilise system. | 1–2 weeks |
| Stocking | 10 | Stock fingerlings (Stage 1) — 150–200 Nile tilapia fingerlings, 5–10cm. Begin feeding at 3% biomass/day. Monitor ammonia daily. | Day 1 of fish |
| 11 | First planting — plant Beds 1–3 (pechay, kangkong, herbs) within 1–2 weeks of fish stocking. | Week 1–2 after stocking |
| Month 2–4 | 12 | First harvest — pechay and kangkong from Beds 1–2. Record yields. Photograph. This is the proof-of-concept moment. | Week 5–6 after planting |
| 13 | Stage 2 stocking — add 150–200 fingerlings (if ammonia has been < 0.5 mg/L for 2 weeks). Plant Beds 4–5 (tomatoes, carrot trial). | Week 6–8 |
| 14 | Comparative water test — test river water downstream of system return point. Compare to pre-build baseline. Document improvement. | Month 3 |
| 15 | DA site visit — invite Department of Agriculture to inspect. Present water quality data, yield records, and system design. Begin discussion of demonstration site status. | Month 4 |
TIMELINE SUMMARY
Pre-build to first harvest: approximately 10–14 weeks. This is aggressive but achievable because the taro pond inoculation advantage shortens the cycling period. The key milestones are: sand tested (Week 0–2), beds built and inoculated (Week 2–4), fish stocked (Week 4–6), first harvest (Week 8–10), DA visit (Week 14–16).