---
title: "Water restoration for RAS operators | Alchemal"
url: "https://alchemal.com/aquaculture/who-we-serve/ras-operators/"
description: "In a recirculating system the biofilter clears ammonia only as fast as its bacteria can breathe. We hold the oxygen nitrification demands, and measure it."
source: "Alchemal — alchemal.com"
---
# Water restoration for 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.

## The problems we see on your water

- [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/)
- [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/)

## What Alchemal installs and takes responsibility for

A recirculating aquaculture system (RAS, where the water is cleaned and reused rather than flowing through once) leans on its biofilter, the bed of media where nitrifying bacteria convert the ammonia fish excrete into far less harmful nitrate. That conversion, nitrification, is oxygen-hungry, so when dissolved oxygen (the oxygen dissolved in the water) at the biofilter runs low, the reaction slows and ammonia climbs.

Nanobubble oxygenation holds oxygen steady to the biofilter and the tanks, efficiently enough that the slow-growing nitrifiers are supplied rather than starved by the faster bacteria competing for it. To be exact about the boundary: this supplies the oxygen nitrification demands, and the bacteria do the removal. Oxygen is not ammonia removal. We install the system matched to the loop at the assessment, and [Stewardship](https://alchemal.com/stewardship/) logs dissolved oxygen at the biofilter and the tanks alongside the ammonia and nitrite you already track. Where a biofilter is undersized or immature rather than oxygen-starved, the assessment says so. The [N-Series](https://alchemal.com/technology/n-series/) unit is matched to the site, and [what we measure and how](https://alchemal.com/technology/how-we-measure/) is published.

## Proof from RAS operators

The first installations for this audience are being instrumented now, and their case files publish when the record is worth reading. The [methodology](https://alchemal.com/technology/how-we-measure/) is already public: what we record, how we calibrate, and how we report what didn't move.

## From your first note to the assessment

1. You describe the water. A specialist reads it, replies in writing, and says whether an assessment makes sense.
2. Your water goes on the schedule. The first assessments and installations are being scheduled now; requests are answered in the order they arrive.
3. The assessment puts a baseline on paper: dissolved oxygen top to bottom, clarity, the condition of the sediment, and a plan with a prediction attached. If oxygenation isn't the right fix, the report says so.

## Questions RAS operators ask

**Does this remove ammonia?**

No, and we are exact about that. Oxygen does not strip ammonia from the water. It lets the nitrifying bacteria in your biofilter process ammonia at their full rate instead of a starved one, so where oxygen was the bottleneck the filter keeps pace. The bacteria do the removal; oxygen lets them.

**Where do you add oxygen, the tanks or the biofilter?**

Both, sized to the demand at each. Nanobubbles put oxygen into the water efficiently and continuously, so a steady supply reaches the culture tanks and the biofilter without the losses of surface aeration. Stewardship measures dissolved oxygen at each so the support is a number, not a claim.

**How is this different from the aeration we run now?**

The difference is transfer efficiency and steadiness. Nanobubbles stay suspended and release oxygen through the water rather than handing it back to the air, so more of what you pay for reaches the nitrifiers, held continuously rather than in bursts.

## Start with a conversation.

Describe the water and a specialist replies in writing, before any commitment. Your water, your numbers.

[Get a free assessment](https://alchemal.com/assessment/?water=ras) [See the case-file format](https://alchemal.com/technology/how-we-measure/)