algae bloom !

please help my tank is driving me mad ! i bought it in december and stocked it in january , we have strugled with amonia due to over feeding which is now under control i have a 100 ltr tank and upgraded the filter to a fluval 205 external 4 weeks ago ,i came home from a week`s holiday 2 week`s ago and my tank has turned green ! the light was on for 12 hours a day i have since reduced it to 9 hours ,i have used green away from interpet twice now last wednsday and again on sunday i have removed 20% of the water each time ,the water is a bit clearer than 2 weeks ago but it is still very green ! please help .jm

In addition to limiting the lightening hours to 8 hours a day maximum,
Keep nitrates, phosphates and silicates at a low level. If you have a persistent problem - use reverse osmosis (RO) or deionised (DI) water, or specific adsorption resins (e.g. PhosGuard). However, note that although high levels of such nutrients may encourage algae, it is not generally possible to completely eliminate algae by attempting to reduce them, as algae can survive at levels below those which can be measured by a hobbyist test kit.
I would Consider adding algae eating fish, such as

the Bushy Nose Pleco http://www.aquariumfish.net/catalog_pages/scavengers/ plecostomus.htm#top2

Siamese Algae Eater http://www.thetropicaltank.co.uk/Fishindx/sae.htm

Chinese Algae Eater http://members.tripod.com/~Boeing_Dude/cae.html

I hope I helped

Do you have live plants in the aquarium? Sometimes live plants will use up the nutrients that the algae need to live. Also, if you float some hornwort on top, it will block some of the light. Another cause of excessive algae is too much sun light. If the aquarium receives much direct sun, it will grow algae like gangbusters.