Onsite ponds - therapeutic or disease vector?

Marty Climenhaga
Marty Climenhaga • 2 June 2024

Question for all - At our older people's mental health unit, we have a lovely little courtyard with a fishpond, a picnic table and plants. It's off the ward, staff use it for lunch and breaks whenever weather is nice. They also bring patients to it to feed the fish and enjoy the garden when able - mostly just in summer and just one at a time as it's a little distance from ward and the ward has its own garden. It's been running this way for years, but a month ago the kitchen manager - who takes care of pond on her own initiative - asked for a small budget to get it cleaned of silt and algae, and the answer came back from the estates manager that they will instead fill it in.  The email said that ponds posed a legionella risk, and 'all independent advice is to remove ponds from healthcare facilities' or something to that effect.  But to me it seems crazy to lose something so valuable for wellbeing of staff and patients, knowing what we do about the benefits of nature engagement. 

i) does anyone know how much of an issue legionella is, or where to find out,  ii)  evidence base on therapeutic ponds, or iii) any other advice, ideas, quick thoughts, shared experience welcomed!  


Comments (4)

James Freeburn
James Freeburn

Hi, legionella can be a massive issue, however as long as there is no chance of the pond water leaking into the clean water system and as long as no-one is touching the water or surround without washing their hands, there shouldn't be an issue.
You could also invest in a Pump filter with UV light (from about £40), as that would reduce the algae and bacteria levels (including legionella).

Luke Hunt
Luke Hunt

I agree this is unlikely to pose significant risk unless the water supply is in direct contact with the pond (unlikely in a healthcare setting). Suggest contacting your local microbiology consultant with responsibility for community infection control if having significant pushback from estates. This is the relevant legislation for water management in healthcare:…

Zak Preston
Zak Preston

There is increased risk of infection from aerosols (e.g. fountains), although NHS guidance on sustainable development actually recommends use of ponds when part of a sustainable urban drainage system (SUDS)…
UHB has a pond on-site so might be worth reaching out to them and some of the case studies on NHS Forest too:…

Kay Stewart
Kay Stewart in 2016 said they did not know of any reported cases of legionnaire's from an outdoor pond. There is a fishkeepers forum that suggests without a waterfeature (that would create an aerosol/spray) the pond would not transmit legionella. A commercial water feature site in America states outbreaks are mostly from indoor (warmer) water features (aerosol/spray/fountains), there are reported cases from outdoor waterfeatures but it seems to be fountains which would create a spray. Good luck

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