Freshwater ich
Watch for: Small white spots, flashing against objects, clamped fins or faster breathing.
First response: Confirm the signs, test water and use a treatment known to be safe for every species in the system.
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Run compatibility check
Cottus gobio
Bullhead
freshwater
Bioload 0.4
Intermediate care
Cottidae
Your complete care profile
Bullhead (Cottus gobio) is a freshwater fish associated with Europe, with a recorded adult length of up to 18 cm. This source-backed catalogue profile brings its essential aquarium planning information together on one page.
Temperature
23–27°C
pH range
7–7.5
Minimum tank
150 litres
Typical lifespan
10 years
Diet
Carnivore
Origin
Europe
Adult size
Up to 18 cm
Care level
Intermediate
Care level recorded in the source-backed catalogue profile.
Aquarium context
freshwater system
Rarely kept; specialist or institutional care may be required
Planning to add Bullhead?
Check it against your aquarium before purchase, then use the complete preparation checklist below.
Check compatibilitySpecies identity
Know the fish
Common name
Bullhead
Scientific name
Cottus gobio
Family
Cottidae
Family group
Sculpins
Water type
freshwater
Native range
Europe
Social planning
Individual assessment
Conservation
Least concern (LC)
Aquarium setup
Build the right system
A fully cycled freshwater aquarium using conditioned water, stable temperature and no detectable ammonia or nitrite.
Use 150 litres as the minimum planning baseline before allowing extra space for a group, tank mates, decor and swimming behaviour.
Hold temperature at 23–27°C and pH at 7–7.5; stability matters more than chasing a single number.
Design the aquarium around the recorded adult length of 18 cm, not the juvenile size seen at purchase.
Provide retreat areas and visual breaks while preserving enough unobstructed space for normal movement and feeding.
Filtration & waste
Lower individual waste load (0.4 index), but group size and total stocking still determine the filter capacity required.
Feeding
Carnivore diet
Offer varied, appropriately sized animal-based foods. Confirm that the fish is eating and avoid relying on a single food long term.
Observe
Confirm every fish reaches food and swallows it.
Control
Stop before leftovers can decay in the aquarium.
Review
Track body condition, waste and feeding response over time.
Behaviour & tank mates
Community planning
Treat temperament as an individual assessment. Observe feeding and territorial behaviour, and keep a safe separation plan available.
No simple community match is approved in this profile. Plan species-only housing or obtain a specialist compatibility assessment before adding tank mates.
No pre-approved tank mate is listed. That is a safety signal, not a claim that every pairing will fail.
Health watch
Recognise warning signs early
These are risks to monitor, not diagnoses. Test the aquarium first and seek an aquatic vet or experienced specialist for severe, fast-moving or uncertain symptoms.
Environmental stress
Watch for: Hiding, faded colour, clamped fins, glass surfing, rapid breathing or appetite loss.
First response: Test water, review temperature and tank mates, reduce disturbance and correct problems gradually.
Before bringing one home
Five-point readiness check
The established aquarium is at least 150 litres and matches the required freshwater system.
Temperature and pH overlap the full 23–27°C and 7–7.5 ranges.
A suitable carnivore food is available and the seller can demonstrate that the fish is feeding.
Ammonia and nitrite test at zero, acclimation is planned and a quarantine or observation option is ready.
Every proposed tank mate has been screened for adult size, behaviour, feeding competition and water compatibility.
Data & source notes
Transparent, in-app data
IUCN LC
Catalogue source
FishBase · release 26.07
Species record
FishBase SpecCode 2439
Aquarium context
Rarely kept; specialist or institutional care may be required
Temperature basis
FishSnap tropical-freshwater planning baseline
pH basis
FishBase stock pH range
Tank basis
FishSnap conservative planning baseline derived from adult size, water type, social ecology and family
Lifespan basis
FishBase wild longevity record
Photo credit
Philip Schaffer · CC BY
FishBase remains an editorial reference, but the useful species and care information is interpreted here so you do not have to leave FishSnap. Conservative planning baselines are labelled as guidance, not guarantees.