The bacteria you cannot see
Fish waste is in the water. Who turns it into plant food?
You can look all day and never see them.
Somebody is doing this job. Where are they hiding?
Have you touched a slippery rock in a stream?
That slime is full of tiny living things.
Some living things are too small to see without a microscope.
Many of them are bacteriaLiving things so tiny you need a microscope to see them.
See it in the glossary. They live almost everywhere.
In aquaponics, helpful bacteria cling to wet surfaces. They live on gravel, roots, and pipe walls.
They form a thin, slimy layer, like the one on the stream rock.
More surface means more room for bacteria. Lots of small, rough stones have lots of surface.
That is one reason many grow beds are full of gravel.
- A · gravel
- B · roots
- C · pipe walls
- D · tank walls
Meet the Recycling Crew: Munchers and Finishers. They are nicknames for two kinds of bacteria.
Each kind does one job, and the next lesson shows you how.
The crew needs air in the water to do its work.
They also need time. A new crew takes weeks to grow big enough.
Your turn. Help the crew or hurt the crew?
Put each card where it belongs.
Does it help the crew or hurt the crew?
Tap a card, then a bin. Or press 1 or 2 on a card.
- Nothing here yet
- Nothing here yet
Does it help the crew or hurt the crew?
The answer:
Helps the crew
- Lots of rough gravel More surface means more room for the crew.
- Air bubbles in the water The crew uses the air to do its work.
- Weeks of time to grow The crew grows slowly, so it needs time.
Hurts the crew
- Strong sunlight on a new system Sunlight can harm a new crew. Growers shade the tank.
- Scrubbing every stone clean Scrubbing washes the crew off the stones.
- Tap water with chlorine in it Chlorine is added to kill germs. It can harm the crew too.
That is why growers clean gravel only when they need to. Scrubbing it knocks the crew off.
They also keep chlorine out of the system.
Check 1 of 3
Where does the Recycling Crew live?
Show the answer
On wet surfaces, like gravel and roots. Right. They cling in a thin, slimy layer on wet surfaces.
Check 2 of 3
What does the crew need from the water to do its work?
Show the answer
Air. Right. They use the air in the water to change the waste.
Check 3 of 3
Why don't growers scrub every stone clean?
Show the answer
They would wash away the crew. Right. The slimy layer is where the crew lives.
You just learned where the bacteria in an aquaponics system live and what they need.
Next up: The nitrogen cycle, step by step.
Go deeper: life in a biofilmOpenClose
The slimy layer has a name: a biofilm. The bacteria live inside a slime they make, which holds them onto a surface.
The bacteria that change fish waste grow slowly compared with many other bacteria. That is why a new system needs weeks before it is ready for fish.
These bacteria do not need light. Sunlight can harm them, most of all while a new crew is forming, so tanks and filters are often shaded or covered.
Many cities add chlorine to tap water to kill germs. Letting the water stand for a day or two lets the chlorine escape, and bubbling air through it helps.
Some cities use chloramine instead. It stays in water far longer, so standing is not enough. Growers ask their water supplier which one they use.
Sources
- Somerville, C., Cohen, M., Pantanella, E., Stankus, A. and Lovatelli, A. Small-scale aquaponic food production: Integrated fish and plant farming. FAO Fisheries and Aquaculture Technical Paper No. 589. Food and Agriculture Organization of the United Nations, Rome, 2014. Link
- Rakocy, J. E., Masser, M. P. and Losordo, T. M. Recirculating Aquaculture Tank Production Systems: Aquaponics, Integrating Fish and Plant Culture. SRAC Publication No. 454. Southern Regional Aquaculture Center, November 2006 revision. Link
- Deer, C., Hu, B., Dunn, B. and Dusci, J. Nitrification and Maintenance in Media Bed Aquaponics. Fact sheet HLA-6729. Oklahoma Cooperative Extension Service, Oklahoma State University, October 2021. Link
- McGee, M. and Cichra, C. Principles of Water Recirculation and Filtration in Aquaculture. FA-12. Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. First published October 1988, reviewed April 2000. Link
- Hargreaves, J. A. and Tucker, C. S. Managing Ammonia in Fish Ponds. SRAC Publication No. 4603. Southern Regional Aquaculture Center, December 2004. Link
- McCoy, G. A. Water quality: Briefing paper on periphyton. Quality of Water Branch Technical Memorandum No. 78.10. U.S. Geological Survey, Water Resources Division, June 22, 1978. Link
- Center for Biofilm Engineering, Montana State University. Biofilm Basics. Link
- MedlinePlus, U.S. National Library of Medicine. Bacterial Infections. Link
- National Human Genome Research Institute. Talking Glossary of Genomic and Genetic Terms: Bacteria. Link
- City of Sioux Falls Water Purification Plant. Chloramines and Fish. Link