Spring stocking is won or lost in the weeks before. Bottom first, then water chemistry, then minerals — why the order of pond preparation matters.
For most Australian prawn and finfish farms, spring is when ponds are filled and stocked for the season. By the time the stock goes in, most of the decisions that shape the season have already been made — in the pond bottom, in the intake water, and in the mineral balance of both. Problems set in during preparation are hard to correct once a pond is stocked and feeding.
The order matters as much as the products. Each stage fixes something the next stage depends on, and doing them out of order means treating the same problem twice.
| Stage | The question | What answers it |
|---|---|---|
| 1 · Dry-out & bottom | Is last season’s sludge still down there? | AQUA OXY, 37–50 kg/ha pre-stocking |
| 2 · Fill | Is the intake water coming in too alkaline? | AQUA pH, 2.5–5 kg/ha per metre of depth |
| 3 · Before stocking | Are magnesium and potassium where the stock needs them? | AQUA ION, dosed against a water test |
1. Start at the bottom
Organic sludge left from last season — feed residue, faeces, dead algae — sits at the sediment, where it goes anaerobic and produces hydrogen sulphide at the interface the stock will live against. Drying out helps, but it does not always finish the job, and the time to deal with it is while the pond is empty or freshly filled, not mid-cycle.
AQUA OXY is a pond-bottom oxidiser for exactly this stage. At 37–50 kg/ha pre-stocking it oxidises accumulated organic sludge: calcium peroxide releases oxygen at the sediment over seven to fourteen days, while coated sodium percarbonate converts hydrogen sulphide to sulphate straight away. It contains no live organisms, so it works regardless of temperature or salinity — useful on a cold spring morning. It is a Class 5.1 oxidiser, so keep it apart from fuels, acids and organics in storage.
2. Then check the water coming in
Much of Australia’s inland and bore water arrives alkaline. If pH and alkalinity are high at fill, they stay high, and the plankton bloom a new pond depends on is harder to establish.
AQUA pH is a 90% citric acid crystal blend for pond preparation. At 2.5–5 kg/ha per metre of depth it brings alkalinity down in pond soil and water. The method is simple: mix the dose in 20 litres of water, soak for 10 to 20 hours, then spread the solution through the pond.
3. Correct the minerals last, against a test
Inland and bore-fed water is typically rich in calcium and short of magnesium and potassium — the reverse of seawater, and the reverse of what a dolomite-based mineral mix corrects. In low-salinity culture a potassium shortfall is acute rather than chronic, which makes it the first thing to check.
That is why AQUA ION is dosed against a measured water analysis, never off a bag. Potassium chloride and magnesium sulphate are supplied separately, by the tonne in bulk bags, and the rate is calculated against seawater ionic ratios for your water. It comes last for a reason: the test is only meaningful once the pond is filled with the water the stock will actually live in.
A short checklist
- →Bottom treated and sludge oxidised before filling.
- →pH and alkalinity measured at fill, and brought into range if high.
- →A full ionic water test taken once the pond is filled — calcium, magnesium and potassium.
- →Minerals corrected against that test, not an estimate.
- →Dissolved oxygen, temperature and pH logged from day one, so you have a baseline before the stock goes in.
For the numbers worth watching once the season is under way, see five numbers that decide a pond season.
What to send us
Send us a recent water analysis, your pond area and depth, what you stocked last season and how the bottom looked at dry-out. That is enough to set rates for each stage — and sometimes to tell you a stage can be skipped. Technical and safety data sheets travel with every order, and the full Aqua range is published.
All Aqua products are for pond and tank water treatment only — not for addition to, or mixing with, feed. Claims are limited to water-quality parameters, and we recommend testing suitability before adopting at commercial scale.