Goldfish tank

[vinrex7]

I have a cold water setup with 2 fish, but after about 1 week the water starts to go green, why is this and can i stop it from happening? (i have a filter in the tank too)

[Rossgo]

i havehe same thing,

what i do is put blue food colouring in the water,

it dont harm the fish at all,

but you do need to clean the tank about every other week too, this help keeps the water and fish clean :)

hope this helps

[Dekay]

The green is algae, it helps if you can position your tank away from sunlight. (algae thrives in sunlight)