---
title: "Water restoration for aquaculture | Alchemal"
url: "https://alchemal.com/aquaculture/"
description: "On a farm, survival and growth ride on the oxygen the water can carry. We bring oxygen through the whole column and record what changes."
source: "Alchemal — alchemal.com"
---
# Water restoration for aquaculture

More of the stock survives, and what survives grows.

In a hatchery raceway or a grow-out pond, survival and growth ride on the oxygen the water can carry, and a stocked system spends it fastest overnight, when nothing is putting it back. Follow one night down the column, and watch where the oxygen goes.

[Get a free assessment](https://alchemal.com/assessment/?water=grow-out-pond) [How restoration works →](https://alchemal.com/technology/nanobubbles/)

## Every animal in the water breathes from it

Stocking density is how many animals a water carries, and a farm carries far more than a pond ever would. Feed goes in through the day, the animals and the bacteria working through their waste both draw dissolved oxygen, the oxygen held in the water itself, and by dusk the water is spending it faster than a diffuser can put it back.

before dawn, the oxygen spent

the same raceway, oxygen held to the floor

*Modeled cross-sections of one grow-out raceway, drawn to one waterline. On the left, the dark layer along the floor is the water where dissolved oxygen runs out first, before sunrise. On the right, the shore unit carries oxygen down the whole column, and the school holds in open water.*

### The bill comes due before sunrise

Through the night there is no photosynthesis to add oxygen back, only respiration taking it away, so dissolved oxygen falls all night and bottoms just before dawn. The animals crowd toward the surface where the last of it is, and a grower can lose a season in one quiet morning. The dark layer that gathers along the floor is the oxygen debt, the water that runs short first.

### The breath goes back in

Nanobubble oxygenation makes bubbles too small to rise, so instead of bursting at the surface within seconds they stay suspended, carrying oxygen through the whole column and down to the floor where the shortage starts. The debt recedes, the water clears, and the school comes back down into open water.

### Oxygen held to the sediment

With oxygen carried the full depth around the clock, the pre-dawn low never reaches the level that stresses the stock, feeding stays efficient, and the water stops setting the ceiling on how many animals it can hold.

## The mechanism on this water

Farmed water fails from the bottom up. The animals, the uneaten feed, and the bacteria breaking down waste all draw dissolved oxygen, the oxygen held in the water itself, and the sediment runs short of it first. Through the night there is no photosynthesis to replace what respiration takes, so the oxygen falls until just before dawn, which is why die-offs arrive in the morning and not at noon.

Nanobubble oxygenation, oxygen in bubbles small enough to stay suspended instead of rising and bursting, carries dissolved oxygen through the whole column and down to the floor where the shortage starts, and adds nothing else. The [technology pages](https://alchemal.com/technology/nanobubbles/) lay the mechanism out, and [how we measure](https://alchemal.com/technology/how-we-measure/) shows the standard every claim on this site is held to. Set against the paddlewheels and diffusers a farm already runs, this is nanobubble aeration, and [how it compares with an aerator](https://alchemal.com/technology/nanobubbles-vs-aeration/) shows where each one fits.

### Dissolved oxygen over one summer day

*Representative values for a productive pond in summer, consistent with published diel dissolved-oxygen studies. A mechanism diagram, not a reading from a named site.*

**View the data**

| hour | dissolved oxygen (mg/L) |
| --- | --- |
| 0 | 7.2 |
| 3 | 5.4 |
| 5 | 4.2 |
| 7 | 5.6 |
| 10 | 8.4 |
| 13 | 11.2 |
| 16 | 12.6 |
| 19 | 10.8 |
| 21 | 9.0 |
| 24 | 7.2 |

## What the published work shows

2×

total harvest

In a controlled shrimp trial, nanobubble aeration roughly doubled total harvest and productivity against a conventional diffuser aerator, and survival reached 95 percent.

[Rahmawati et al., *Aquaculture and Fisheries*, 2021](https://doi.org/10.1016/j.aaf.2020.03.005)

Pacific white shrimp (Penaeus vannamei) in 50 m² indoor raceway ponds over 81 days, nanobubble versus diffuser aeration. A controlled trial, not an Alchemal installation.

These findings describe nanobubble oxygenation as a mechanism, not an Alchemal unit. Our own installations publish their records as case files as they go in.

## The problems we treat here

- [Morning die-offs: the pre-dawn oxygen crash Stock lost overnight, found at first light. See what causes the pre-dawn oxygen crash and how a continuous reserve prevents the next one.](https://alchemal.com/problems/morning-die-offs-grow-out-ponds/)
- [Low dissolved oxygen: the ceiling on stocking density Feeding harder for gains that don't come, with the pond closer to a crash each night. Oxygen is usually the ceiling. See how to read the headroom.](https://alchemal.com/problems/low-oxygen-stocking-density/)
- [Fish that eat but don't grow: feed, oxygen, and FCR Feed going in without the weight coming out. When oxygen is marginal, the stock converts poorly. See how steadier oxygen returns energy to growth.](https://alchemal.com/problems/feed-conversion-slow-growth/)
- [Living on paddlewheels: cost, coverage, and the outage risk Paddlewheels running long hours, more added every season, one outage from a bad night. See how a held reserve changes what the machines must carry.](https://alchemal.com/problems/paddlewheel-aeration-dependence/)
- [Black pond bottoms in shrimp culture: the anaerobic sediment A pond bottom gone black and sour, with soft-shelled shrimp and thin survival. See how oxygen to the sediment keeps the bottom aerobic.](https://alchemal.com/problems/black-pond-bottom-shrimp/)
- [Hatchery and raceway oxygen: the flow-through margin Dissolved oxygen falling pass to pass, the last raceway running short. See how efficient oxygen widens the flow-through margin.](https://alchemal.com/problems/hatchery-raceway-oxygen/)
- [Biofilter oxygen and ammonia in RAS: the nitrification link Ammonia creeping up while the biofilter looks healthy. Nitrification is oxygen-limited. See how steady oxygen lets the biology keep pace.](https://alchemal.com/problems/ras-biofilter-oxygen-ammonia/)

## From the field notes

- [The operator's desk How to read a raceway's overnight oxygen log The overnight dissolved-oxygen log records the after-dark draw and the pre-dawn sag. Reading it is how you see a fish kill coming.](https://alchemal.com/field-notes/reading-a-raceway-overnight-oxygen-log/)

## Who we serve

- [Shrimp farmers A crash before dawn, a black bottom by mid-cycle, a feed bill that climbs while growth stalls. In grow-out the margin lives in the overnight oxygen, and one hot night can take a season's work. You want numbers, not adjectives, which suits us.](https://alchemal.com/aquaculture/who-we-serve/shrimp-farmers/)
- [Hatcheries In a hatchery the value per animal is highest and the tolerance for a bad night is lowest. Larvae and fingerlings feel a swing in oxygen before anything else does, and a few hours of low water can undo weeks of careful work.](https://alchemal.com/aquaculture/who-we-serve/hatcheries/)
- [Raceway operators On flow-through raceways the water arrives rich and leaves used, and the last pass runs the tightest margin. Carrying capacity is set at the lowest-oxygen point, and trout or catfish crowd it whenever a warm spell thins the source.](https://alchemal.com/aquaculture/who-we-serve/raceway-operators/)
- [RAS operators In a recirculating system the margins are tight and the biology is unforgiving. When the biofilter runs short of oxygen, ammonia creeps up and the whole loop feels it, and a water change spends the heated, conditioned water the design exists to keep.](https://alchemal.com/aquaculture/who-we-serve/ras-operators/)

## The N-Series fit

The [N-Series](https://alchemal.com/technology/n-series/) is one platform, sized by the volume of water it has to oxygenate rather than by the kind of farm. A small hatchery raceway or a nursery tank sits in the range the [N1](https://alchemal.com/technology/n-series/n1/) covers, to about a quarter acre of surface; a grow-out pond up to a few acre-feet, the volume of water one acre holds at one foot deep, sits in the [N2](https://alchemal.com/technology/n-series/n2/) range. Larger ponds and multi-pond sites step up from there. An assessment sizes the unit to the water and where it installs.

## How it works

1. 1

   ### Tell us about your water

   Describe the problems you are facing, and we work with you to find out whether Alchemal is the right solution for your water.

   [How the assessment works →](https://alchemal.com/assessment/)
2. 2

   ### Install the unit

   The N-Series unit goes in at your water and gets to work: oxygen through the whole column, and sensors that let you watch the response.

   [The N-Series line →](https://alchemal.com/technology/n-series/)
3. 3

   ### Partner for the long term

   We stay with you to keep the water improving, the unit running well, and the results where you want them.

   [What Stewardship covers →](https://alchemal.com/stewardship/)

[Get a free assessment →](https://alchemal.com/assessment/)

## Tell us what your water is doing.

Describe what you are seeing, and a specialist will help you determine whether Alchemal can help you fix it, before any commitment.

[Get a free assessment](https://alchemal.com/assessment/?water=grow-out-pond) [How restoration works](https://alchemal.com/technology/)