As much as i understand trying to do things on a budget, You are dragging alot fo wattage through those Cheap cords ! Becareful folks, More household fires are started every year from overloaded circuts!
There are other products out there that are designed to contol your lighting and such, do a search for Reef keeper! Yes it costs more, But it is designed to do excatly what you are trying to do!
The way i see it, you've already invested more into you tank then you should have!
Take care of your investment!