# In a 392-patient dental clinic trial, adults waiting near fish rated the room more favorably, but the aquarium did not measurably lower anxiety, mood scores, blood pressure, or heart rate before treatment

> Three hundred ninety-two adults sat through a real-world test of a familiar idea in healthcare design: if people watch fish before a stressful appointment, will they actually feel calmer? The answer from this study was mixed. Patients in a Zurich dental clinic...

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Published: 2026-08-15T03:30:02+00:00
Categories: Explainer, Health

![A male dentist consulting a female patient at a modern dental clinic reception](https://www.argo.net/wp-content/uploads/2026/08/dental_waiting_aquarium.jpg)

Three hundred ninety-two adults sat through a real-world test of a familiar idea in healthcare design: if people watch fish before a stressful appointment, will they actually feel calmer? The answer from this study was mixed. Patients in a Zurich dental clinic did seem to like the room with fish better, yet the main measures of stress and anxiety did not move in a meaningful way.

In the trial, published in [**PLOS ONE**](https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0258118), researchers at the **University of Zurich** compared a standard waiting room, a tank without fish and a fully stocked tank with **Malawi cichlids**. Adults waited for **20 minutes** before treatment, while the team tracked **blood pressure**, **heart rate**, anxiety, mood and how patients judged the room itself. The central result was simple: a more pleasant room did not automatically produce calmer bodies or lower anxiety scores.

## Why the idea seemed worth testing

Dental clinics have good reason to care about what happens in the waiting room. Anxiety often starts before a patient ever sits in the treatment chair and that early tension can color the whole visit. Designers and clinicians have long looked for small changes that might soften the experience without medication, extra staffing, or a longer appointment.

Fish tanks have carried that promise for years. The paper points to earlier work suggesting that interaction with animals can reduce stress in some settings and it also cites a [systematic review](https://doi.org/10.1371/journal.pone.0220524) that found the evidence around fish and aquariums remains limited and uneven. Some studies reported relaxation or better mood after people watched fish, including an earlier [aquarium dose-response study](https://doi.org/10.1177/0013916515597512), while other trials found little or no measurable benefit.

That uneven record is exactly what makes this dental study interesting. It did not ask whether aquariums are charming in a general sense. It asked a tougher question: when adults are already waiting for dental care, does a real aquarium change the numbers that usually stand in for stress, or does it mainly change how the environment feels?

## How the clinic set up the test

The researchers ran a **controlled clinical trial** in a geriatric and special-care dental clinic in Zurich, Switzerland. Adults 18 and older could join if they gave informed consent. The study protocol was logged in a [**ClinicalTrials.gov** record](https://clinicaltrials.gov/study/NCT04630600) and the report says the team followed [CONSORT guidelines](https://www.bmj.com/content/340/bmj.c332) when describing the trial.

Patients did not all enter one big mixed pool at the same time. The clinic first enrolled people into a control group with no aquarium. After that phase ended, the clinic installed a tank with water and decorations but no fish. Only in the last phase did patients wait beside a fully stocked aquarium. The article describes the study as single-blinded and non-randomized, which matters because the sequence of enrollment can make group comparisons less secure than in a randomized design.

Each participant had blood pressure and pulse measured on arrival and again after 20 minutes in the waiting area. The team also used the **State-Trait Anxiety Inventory** short form, along with mood scales for pleasantness and arousal. A separate five-question survey asked patients how they felt about the waiting room itself. That last survey turned out to be where the aquarium showed its clearest advantage.

## What the numbers showed

A total of 7,581 prospective participants were screened. Of those, 431 consented and 392 completed the trial, with a mean age of 65.07 years. Across all groups, blood pressure and heart rate changed over time while people waited. That means waiting itself was associated with some movement in the physiological measures. What the study did not find was a meaningful extra benefit tied to the aquarium condition for blood pressure, anxiety, or mood.

The heart-rate results were a little more complicated, but they still did not support a clean aquarium effect. The paper reports an overall group effect for heart rate, yet there was no time-by-group interaction, which is the pattern that would have helped show that one waiting-room condition changed patients differently over the waiting period. The authors therefore did not treat the fish tank as a demonstrated cause of calmer physiology.

Anxiety and mood scores were also stubbornly similar across the groups. Patients who waited with fish did not post clearly lower results on the anxiety scale and they did not show a verified lift on the mood measures used in the trial. The strongest positive signal came from the room-rating questionnaire, the study's measure of **waiting area experience**: people judged the fully stocked aquarium setting more favorably than the alternatives. In plain terms, patients liked the fish tank, but liking the room was not the same thing as scoring lower on anxiety before care. The difference matters because a pleasant environment can improve the texture of waiting without changing the clinical stress markers researchers chose to track.

## Why people may enjoy the room without showing lower anxiety scores

That split between preference and measurement is the most human part of the study. A waiting room can feel warmer, more interesting, or less sterile without changing a person's internal state enough to register on clinical scales. Someone may look up, watch fish move through the tank and decide the room is nicer, while still carrying the same worry about injections, drilling, bad news, cost, or loss of control.

The authors offer several reasons for the mismatch. Exposure time may have been too short or too diffuse. In some earlier studies, participants were asked to focus on an aquarium for a set period. Here, patients were simply in the room and free to attend to anything around them. A fish tank cannot hold full attention when forms need signing, appointments are on the mind and dental treatment is minutes away.

Age may also matter. The average participant in this trial was older than the young adult groups in several earlier studies that reported stronger positive effects. The paper also notes that some benefits in prior aquarium research appeared in very different populations, including people living with dementia. Put another way, the emotional setting, the age mix and the reason a person is present may all influence whether watching fish becomes calming, merely pleasant, or functionally irrelevant.

## What the limitations mean for real waiting rooms

The study does not close the case against aquariums in healthcare. It sets a boundary around what this particular clinic could show. Because the groups were enrolled one after another rather than randomized together, the comparison is more vulnerable to hidden differences between phases. The authors also say some outcomes were underpowered, with post hoc calculations implying that much larger samples would have been needed to reliably detect very small effects for several measures.

Room design still matters, but this paper suggests that its influence may work first through comfort and perception rather than through immediate changes in standard stress markers. A calmer-looking space may support dignity, patience and willingness to wait even when it does not lower questionnaire scores or vital signs in a detectable way. For clinic managers, that is a useful distinction. A room can improve experience without becoming a proven anxiety treatment.

Future studies could test the same idea under tighter conditions: randomize patients, track exactly how long they watch the tank, compare older and younger adults separately, or measure whether stronger effects appear during longer waits. Until then, the clearest factual takeaway is modest and practical. In this trial of adult dental patients, fish made the waiting room more appealing, but the aquarium did not deliver a verified drop in pre-treatment stress, anxiety, mood disturbance, blood pressure, or pulse.