"Bubba Wood" wrote...

So my neighbor asks me to look at his kids desk to see if I know how
to fix it. He had a 10 gal aquarium on it for about a year with a
towel between the tank and the desk top. There are black spots and
streaks in the top where moisture was trapped.

The top is MDF core red oak veneer with what looks like about a 1/64"
thick veneer.
[...]

Oxalic acid bleach is usually used to remove black stains from oak.
Available at any hardware store.

Try stripping the finish, let dry, bleach with oxalic acid solution, let
dry, sand ever so gently by hand with 150 or 180, stain and finish.



--
Timothy Juvenal
www.tjwoodworking.com