Goldfish
may


only


grow

to


sexual


maturity

with


enough


water


and

the


right


nutrition.


Most


goldfish


breed

in
captivity,

particularly


in


pond


settings.


Breeding


usually

happens


after


a

significant


temperature


change,

often
in

spring.


Males

chase

females,


prompting


them

to


release


their


eggs

by

bumping


and

nudging

them.
Goldfish,

like


all


cyprinids,


are


egg-

layers.


Their


eggs

are


adhesive


and

attach


to


aquatic


vegetation,


typically
dense

plants

such

as

Cabomba


or


Elodea

or


a

spawning


mop.


The


eggs

hatch


within

48

to


72

hours.
Within

a

week


or


so,


the


fry

begins


to


assume


its

final


shape,


although


a

year


may


pass

before


they


develop


a
mature
goldfish


color;


until


then


they


are


a

metallic


brown


like


their


wild


ancestors.


In


their


first


weeks


of


life,
the

fry

grow

quickly—an

adaptation

born


of


the


high


risk

of


getting


devoured

by

the


adult


goldfish


(or


other


fish
and
insects)


in


their


environment.
Some
highly

bred


goldfish


can

no

longer


breed

naturally


due

to


their


altered

shape.


The


artificial


breeding
method

called

"hand


stripping"


can

assist

nature,


but


can

harm

the


fish

if

not


done


correctly.

In


captivity,


adults
may

also


eat


young


that


they


encounter.
Mosquito

control
Like

some


other


popular


aquarium

fish,


such

as

the


guppy,


goldfish


and

other


carp


are


frequently


added


to
stagnant

bodies


of


water


to


reduce

mosquito

populations.


They


are


used

to


prevent


the


spread

of


West


Nile
Virus,
which

relies


on

mosquitoes

to


migrate.


However,


introducing


goldfish


has

often


had

negative
consequences

for


local

ecosystems.
Controversy

over

proper

treatment
Some
countries

ban

the


sale


of


traditional


fishbowls

under

animal


welfare
legislation

due

to


the


risk

of


stunting,


deoxygenation


and

ammonia/nitrite
poisoning

in


such

a

small


environment.


Because


of


their


large


oxygen


needs


and
high

waste

output,

such

bowls

are


no

longer


considered


appropriate

housing


for
goldfish
In

many


countries,


carnival]


and

fair


operators


commonly

give


goldfish


away


in


plastic


bags

as

prizes.


In


late
2005

Rome

banned


the


use

of


goldfish


and

other


animals


as

carnival


prizes.


Rome

has

also


banned


the


use
of

"goldfish

bowls",


on

animal


cruelty


grounds.
BBC
News


Online


-


Goldfish

are


no

longer


to


be

given


as

prizes

though

this

has

since


been


amended

to


only
prevent

goldfish


being


given


as

prizes

to


unaccompanied

minors.
In

Japan,


during


summer

festivals

and

religious


holidays

(ennichi),


a

traditional


game


called

goldfish


scooping