Make your own oxygen, on site.
A PSA generator separates oxygen from compressed air, so the farm stops depending on liquid oxygen deliveries. Below: how to size it on feed, what to ask about purity and output, and how to plan the backup.
oxygen from air
sets the size
designed per site
power supply
Oxygen-rich gas from air. Not pure oxygen.
Air is about 21% oxygen. A PSA generator pushes compressed air through a sieve that holds nitrogen back and lets oxygen through. Makers typically state purity up to about 95% (). The rest is mostly argon and some nitrogen, which is why purity matters when you size the cones.Pneumatech
- oxygen-rich gas, continuously, as long as it has power and clean dry airMakes:
- oxygen cones or other dissolvers that put the oxygen into the waterFeeds:
- dissolve oxygen itself, remove CO₂, or keep running in a power cutDoes not:
Five parts, one chain.
Each part can limit the output. A generator is only as reliable as the air that goes into it.
Air compressor
Supplies compressed air
Overheats in a hot, closed room; worn compressors lose output
Air treatment
Removes water, oil and dust before the sieve
Wet or oily air damages the sieve and lowers purity
Two sieve beds
One bed holds nitrogen while the other is purged; they alternate
Sieve contaminated or worn: purity drops
Buffer tank
Smooths flow and pressure to the cones
Undersized tank gives unstable supply at peak
Oxygen outlet and controls
Flow and purity to the cones, with alarms
No purity alarm means low purity goes unnoticed
From feed to generator, in five steps.
Oxygen demand follows feed, not tank volume. Any supplier should show you these steps for your farm.
Oxygen the fish use
A common rule of thumb is about 350 g of oxygen per kg of feed for the fish to use it. Use peak daily feed.
Oxygen the bacteria use
The biofilter and other bacteria add their own demand, about 20–30% of a system’s total by one estimate.
Peak hour, not average
Fish use most oxygen in the hours after feeding. The generator is sized on that peak hour.
Dissolving losses
Not every gram reaches the water. Divide by the transfer efficiency of the cones or diffusers it feeds.
Margin and backup
Add margin for growth, then size a backup supply for the hours the generator could be down.
Sources: rule of thumb for fish oxygen use from ; bacterial share from .NovairThe Fish Site
A worked example
A farm feeding 500 kg a day needs about 175 kg of oxygen a day for the fish alone, before the bacteria. Spread evenly that is about 7 kg an hour, but the hours after feeding need more, so the generator is sized above the average. Illustrative figures, not a quote.
Four numbers to ask for.
Generator ratings are not always stated the same way. Ask every supplier for these, so you compare like with like.
Output in kg of oxygen per hour, at a stated purity
Output falls as purity rises. A rating without its purity cannot be compared.
Purity at full output
Running a generator past its rating lowers purity, and lower purity means more gas through the cones.
Energy per kg of oxygen, including the compressor
Energy is the running cost. One maker publishes 0.55 kW per kg at 93% purity (); ask how each figure was measured.SeafoodSource
Rated ambient temperature
Compressors and sieves lose output in a hot plant room. Check the rating against your site.
Most farms end up with both.
PSA generator
No deliveries; supply follows your schedule
Needs power and maintenance; purity below liquid oxygen
Main supply on most sites
Liquid oxygen tank
Higher purity; works without power for production
Depends on deliveries and a supply contract
Main supply where deliveries are reliable, or backup
Oxygen cylinders
Simple, no equipment to run
Small volume, many changes
Short-term backup, small farms
A PSA generator stops in a power cut. Plan the backup on how many hours the farm must survive without the generator, and make the changeover automatic.
When dissolved oxygen falls.
Purity falling
Wet or oily air reaching the sieve, or demand above the rating
Air dryer and filters; demand against rated output
Output or pressure low
Compressor wear, a blocked filter, or a leak
Compressor hours; filters; leaks in the oxygen line
Generator stops on alarm
Power, or compressor overheating
Plant room temperature and ventilation; alarm log
Oxygen flowing but tank oxygen low
Dissolving problem, or demand above design
Cone flow and pressure; feed rate against the design
Backup did not start
Changeover not automatic or not tested
Test the changeover on a schedule
We size the oxygen with the fish and the cones.
A generator bought on its own is sized on a number someone gave the supplier. We size it from your feed plan, together with the cones, degassing and backup.
Sized on peak feed
Fish and bacteria demand, at the peak hour, with the calculation sent to you.
Backup designed in
Backup oxygen sized on the hours your site must cover, with automatic changeover.
Fitted and tested
Supplied, fitted and tested with the rest of the system before it ships.
Your voltage
220, 380 or 110 V, matched to your site supply.
What we confirm per project.
Function
Produces oxygen-rich gas on site from compressed air
Feeds
Oxygen cones
Output and purity
Confirmed per model, at stated purity
Sizing
Peak oxygen demand from feed, with margin
Backup
Standby oxygen supply designed per site
Voltage
220, 380 or 110 V
Model output, purity, power and dimensions are listed in the datasheet. We confirm the model against your oxygen demand before quoting.
It follows peak oxygen demand, which follows feed and temperature. Roughly, the fish need about 350 g of oxygen per kg of feed, plus what the bacteria use, sized on the peak hour. We do the calculation in the first layout.
Yes, for dissolving into fish water with cones. Lower purity just means more gas volume for the same oxygen, so the cones are sized for it.
The generator stops. Fish keep using oxygen, so the backup must start on its own. We size it on how long your site can be without power.
PSA suits most sites as the main supply because it removes the dependence on deliveries. Liquid oxygen or cylinders make a good backup.
Mostly the compressor and the air treatment: filters, drains and dryer. Clean, dry air keeps the sieve working.
In a ventilated, cool plant room. Heat lowers compressor output and shortens its life.
Yes. Tell us the cones you have and the flow through them, and we check the generator against them.
Ozone generators are often fed with oxygen. If you plan ozone, tell us, and we include its gas demand.
Send your feed plan. We size the oxygen supply.
Peak daily feed, water temperature and how long your site can be without power. We return the generator size, cones and backup.
- Sized on peak feed
- Bacteria demand included
- Backup sized per site
- Fitted and tested with the system