Aquariums and well-being: what research shows

1. People prefer a room with an aquarium in it, and say so reliably

Measured

Lundberg and Srinivasan asked 392 geriatric dental patients to rate a waiting room.² The room with a stocked tank was rated significantly higher than the same room with an empty tank and than the same room with no tank, at p below 0.001. In that same trial blood pressure, heart rate, anxiety and mood were all unchanged. This is the only claim in the field with a properly powered study behind it, and it is a claim about the room rather than about the person.

2. People watch a tank about twice as long once it has fish in it

Measured

At the National Marine Aquarium in Plymouth, Cracknell and colleagues timed 112 visitors without their knowledge while one large exhibit was being restocked. Mean time spent looking was 3.01 minutes at the empty exhibit, 4.08 minutes partly stocked and 5.94 minutes fully stocked. F(2, 109) equals 10.15 at p below .001, with a partial eta squared of .157.³ That is the largest effect anywhere in this literature and it is a measurement of behavior rather than a claim about a mechanism. Going from partly to fully stocked was not significant at p equals .065, so past a point more fish stops helping.

3. Ten minutes in front of a tank is followed by a small fall in heart rate

Measured

In the same Plymouth work, heart rate fell by about 6 beats per minute at the fully stocked exhibit, about 5.5 partly stocked and about 2.2 at the empty one. The effect of stocking level was significant at p equals .039 with a partial eta squared of .053, which is a small effect, from a study of 84 students that could not randomise people to conditions and has never been repeated.³ In the larger dental study the group sitting in front of no aquarium at all had the largest fall of the three, after twenty minutes of simply sitting in the waiting area.² Sitting still does much of this. The ten minutes belongs to the Plymouth study; the twenty belongs to the dental one, and the two should not be run together.

in the field does not say what it is cited for

Katcher and colleagues, 1984, is the study behind almost every "aquariums lower blood pressure" line you will read.⁴ It measured anxiety with a blind observer and found no significant effect. It measured blood pressure and found no significant effect. It collected heart rate and never reported it. There were eight people per cell, and the paper's actual subject was hypnosis.⁴ What it did find was that people rated the room as more comfortable, which is a real result and a much smaller one than the sentence it is used to support.

And a dog beat a tank in the same clinic in the same year

Barker's group ran two studies in one setting. The dog cut patients' fear by 37 percent at p equals .0006.⁵ The aquarium moved nothing at all.⁶