Fish Tanks And Windows

[Myriad2112]

My fishtank used to look dirty enough to clean every 2-3 months. I have recently moved it across the kitchen to near the window and now the glass becomes thick with green and brown algy every 2-3 weeks. It's not in direct sunlight but behind the curtain. Why would this happen?

[SlackAlice]

Despite your best efforts you are exposing the fish tank glass to higher levels of light, encouraging growth of algae.

[B00]

When you say clean every 2-3months...

You do water changes more often than that in the meantime though right?

And yes Alice is right, too much sunlight.

[SlackAlice]

Also, to add to BOO and my earlier post, have you got any lighting fitted and how do you regulate it?

[Myriad2112]

Ahhh, I wasn't sure if that might be the problem. I top the water up but I don't change it. There are only two little goldfish in there and they seem quite happy

[Myriad2112]

There is a light which I put on at night for 1-3 hours. They seem to like it :-)

[jomifl]

The increased algae growth will remove the fish waste products from solution which isn't a bad thing as long as you remove the scaped off algae from the tank. Why not put some black paper between the tank and the window to reduce the light level.

[Avatar]

Topping up the water isnt enough. You ought to change 10-20% per week or 25 - 40% every few weeks. Making sure of course that the water you put in is the same temperature as the tank water and that it has been treated with a chlorine/chloramine remover first. Your fish may be surviving on your current method but they won't be thriving.
As has been said, natural light on the tank causes terrible algae. Try black card or tin foil shiny side out on the back of the glass maybe.