A laser pointer on the aquarium glass: what the researchers actually saw
Published by Planète Pets · managing editor: Clément Lacaille · how our guides are written
The idea keeps coming back on forums: cats chase a red dot, so why not fish? An American team took the question seriously and measured it in pet shops, pointer in hand. Our occupation guides are gathered in the fish toys and enrichment section.
Contents · 5 sections
What 66 species did in front of a moving dot
Eisenbeiser, Serbe-Kamp, Gage and Marzullo published an open-access exploratory study in Animals in 2022, run over seven visits to three shops, on sales tanks from 15 to 240 gallons (see the study). The pointers were off-the-shelf models sold as cat toys, in red, green and blue.
- 58 species out of 66 (88%) reacted: 15 strongly, 28 moderately, 15 weakly. Eight species did nothing at all.
- "Strong response" had a precise definition: chasing the dot for at least five seconds.
- 34 species out of 66 responded to red only; two to green alone, one to blue alone.
- Among the indifferent: the betta, the rummy-nose tetra, the Jack Dempsey. The goldfish is a borderline case — depending on the tank it did nothing, or at most turned towards the dot.
- Among the keenest: the tiger barb, the platy, the clownfish, the rainbow shark, the royal gramma.
A "toy" that does not last
The authors then set the whole thing up at home. Eight tiger barbs followed for five weeks stopped caring after roughly two weeks, whatever the colour. Of three Tropheus duboisi cichlids watched for ten weeks, only one ever responded. A telling detail: those same tanks held weighted self-righting thermometers, in an attempt to reproduce the famous object play described in this species by Burghardt, Dinets and Murphy in 2015 — over ten weeks, the fish never touched them.
Why this does not mean fish play
The authors themselves decline to settle it: these reactions could, they write, be conceived as "play-like", but equally as an investigatory response toward a novel stimulus, and their results offer no definitive conclusion. Add that the observations took place in sales tanks sometimes holding a hundred fish, often recently arrived. There is no statistical test in that arm of the study: these are by-eye ratings on four levels. And beware the shortcut on colour: the three pointers were never measured or calibrated, so "red works better" says nothing about fish vision, only about those three objects. Our article on aquarium light colour deals with a quite different question, that of permanent ambient lighting.
Should you avoid it?
The study reports no disorder, but across eleven fish followed for five to ten weeks depending on the species, and without a single physiological measurement: far too thin to call it harmless. The authors themselves point to work by Kogan and Grigg published in 2021, which found in cats an association between laser play and abnormal repetitive behaviours — a self-reported, correlational survey on another species, but one that invites caution with a stimulus that can never be caught.
- Never aim at the eyes, and keep the dot on the substrate or the glass, as the authors did.
- If your fish is a betta, the study suggests skipping it: look instead at mirrors for bettas, and for a goldfish at suitable enrichment.
- The documented alternative remains learning, covered in our article on cognitive training in fish.
Frequently asked questions
My fish ignores the dot — is something wrong?
No: eight of the sixty-six species tested showed no reaction at all, and within a species not every individual responds — only one of the three cichlids followed at home ever did.
In our shop, for this use: Stick-on digital thermometer for aquarium and terrarium glass (€18.90) · the whole shop
This guide is part of Planète Pets’s Fishkeeping universe. Our advice is general in nature: for any health concern, your veterinarian remains the only reference.