Green Water O.o

[Starfirefly26]

Eeep! The water in my 10g is all green.
I've recently changed from an undergravel filter to a normal one, and changed substrate to sand.

Of course, the water is green, and theres becoming an algae issue. The surface of the sand is all brownish, and theres both green and brown algae on the sides.

Will a major water change (like 90%) fix this, along with removing the 'infected' layer of sand and scrubbing down the sides?

All I can think of that would cause this was a power outage a couple weeks back (it's been green for a while, a small water change did nothing and neither did time), when the power was out a couple of hours before my dad hooked it up to a tiny generator for the filter.

All the fish look to be perfectly healthy, like nothing has happened, but I just don't feel right with icky green water. >.<

 

[Rodders]

You'll have to do 50%, cover tank for 2-3 days, complete darkness and then another 50% after that.
That should do it.

 

[Lynden]

I had the same problem with the marine tank... one can't believe how bad it could possibly be at the worst of it until one has seen it.

I tried darkening the tank, but the problem was removed very quickly with the addition of a UV sterilizer. Make sure to have plenty of filtration; if not, a layer of dead will pile up on the substrate.