Guppies: how much enrichment does the tank actually need?
Published by Planète Pets · managing editor: Clément Lacaille · how our guides are written
"Enrich the tank" gets repeated constantly, rarely with a measure of how much actually makes a difference. A study by Manenti, Sicuro, Macchi, Ponzio, Crosetto, Cavallari, Tarantola and Mugnai, published in 2025 in Frontiers in Fish Science, compared three decor levels in guppies (Poecilia reticulata): no enrichment, 25% coverage, and 75% coverage (see the study). Practical guidance is gathered in our toys and enrichment section.
Contents · 4 sections
Fifteen tanks, three decor levels, one protocol
The authors split fifteen aquariums across the three coverage levels (plants, wood, structures), then filmed the fish to analyse behaviour and measured cortisol directly from tank water — a method that avoids handling the guppies to sample them.
More decor, more natural behaviour
In the most enriched tanks (75%), behaviours linked to good quality of life — feeding on wood and plants, staying near the surface, courting — were markedly more expressed than in the poorer tanks. Conversely, stereotypy, a classic indicator of chronic stress in captive fish, was significantly more common in tanks with no enrichment.
A side effect worth knowing before decorating everything
The result is not one-sidedly positive: biting between individuals was also more frequent in the most enriched tanks, likely linked to heightened territoriality once structures carve out zones worth defending. Enrichment reduces diffuse stress but can favour more localised friction — a trade-off to watch rather than a case against decor.
- Tanks with no enrichment: more stereotypy (a chronic stress indicator).
- Tanks at 75% coverage: more feeding on wood/plants, courting and surface time.
- Trade-off: more biting linked to territoriality in the richest tanks.
- Waterborne cortisol allowed stress to be measured without handling the fish.
For a community guppy tank, the practical approach is to aim for generous decor — close to the 75% tested — while spreading it across several hiding spots rather than one dense zone, to dilute territorial encounters. Our article on floating plants and the one on hiding spots for stressed fish cover how to spread this kind of structure. Stocking itself comes first, though: our guide to community versus species-only aquariums helps settle that question before decor even comes into play.
Frequently asked questions
What does 75% coverage actually look like?
The share of the tank's footprint taken up by decor — plants, wood, rocks — seen from above, as opposed to mostly open water.
Does more biting mean less enrichment is better?
Not necessarily: the study shows a trade-off, not a failure of decor. Spreading several zones rather than one concentrated area limits this risk while keeping the stress benefits.
Does this apply to fish other than guppies?
The protocol was run on guppies. The general principle — more structure, less stereotypy — is consistent with other studies in captive fish, but the 25% and 75% thresholds are specific to this species.
In our shop, for this use: Resin shipwreck hide for aquariums, 4 models (€26.90) · 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.