Does a simple PVC pipe in the tank reduce zebrafish stress? What a study found
Published by Planète Pets · managing editor: Clément Lacaille · how our guides are written
Tank enrichment is often said to reduce fish stress, but the protocols tested in the lab are often too elaborate to replicate at home. A study by Gazzano, Di Filippo, Licitra, Ogi, Fronte, Curadi and Gazzano, published in January 2025 in Veterinary Sciences, tested enrichment as simple as a PVC pipe in zebrafish (, doi 10.3390/vetsci12010038). Our enrichment ideas by animal are gathered in the fish toys and enrichment section.
Contents · 5 sections
A T-shaped pipe, for three months
Four control shoals and five "enriched" shoals, of eight fish each, were tracked for 90 days. The enriched shoals had access to a simple T-shaped PVC pipe, 11.7 cm long and 4 cm in diameter — the only difference from the control tanks, which were left bare. At the end of the 90 days, all fish were moved to a new, unfamiliar tank for a shoaling test, with cortisol released into the water measured before and after the test.
What the move to unfamiliar surroundings reveals
Distance moved, swimming speed and shoal acceleration showed no difference between the two groups. Physiologically, though, only the control group showed a significant cortisol rise after the transfer; fish raised with the pipe showed no such increase. Behaviourally, both groups drew closer together in the second half of the test — a typical tightening of the shoal when facing an unfamiliar environment — but the enriched fish kept greater spacing between individuals than the controls.
What this study does not show
It compares minimal enrichment against no decor at all, not different levels of enrichment against each other: there is no way to tell whether an extra pipe, or richer decor, would do better still. The protocol covers zebrafish in small laboratory groups, not the mixed community tanks typical of home fishkeeping.
What this means in practice
The most actionable point is almost disappointingly simple: it is not about piling on decor, but about providing at least one structuring shelter permanently in the tank. A simple hiding spot — a tube, half a terracotta pot, a suitable 3D-printed structure — may be enough to soften the stress response to an unpredictable event such as a tank change or the arrival of new tankmates. Our guide on hiding spots and enrichment for stressed fish covers other options.
Frequently asked questions
Does a tank need several pipes or hiding spots?
This study tests only one per tank and does not compare different quantities; it only shows that minimal enrichment beats none at all.
Does this result apply to goldfish or bettas?
The study specifically covers shoaling zebrafish; the effect in less gregarious species remains to be checked. Find all our guides on the fishkeeping hub.
An accessory from our shop for this use: Mini USB aquarium air pump with tubing and air stone (€22.90) · 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.