, drilling the 10 would be the best route to take. I wouldn't use anything much larger than a Maxi Jet 1200 to supply the water to it...a 10g tank doesn't offer much space and you don't want Niagra Falls in there. In this case, as fishfreek said, you'll need to position the fuge a little higher than the sump.
Using a pump to send water to the fuge and another to pump water out of the fuge is not an option because you'll never be able to perfectly balance the flow from the pumps...one will eventually outrun the other one.
Should you decide to go the siphon route, I think you'll have to have an internal overflow box in the fuge and another box in the sump. Just having a siphon presents much the same problem as the two pumps...trying to balance the pump output with what the siphon is draining. You'd also have to run the water level pretty high in the sump to prevent the siphon from breaking. Having the box in the sump insures that there is a constant water level for the siphon tube and will lower the chances of breaking the siphon.
If you put a DSB
in the fuge, I would keep it about 4". As was mentioned above, a 6" sand bed won't leave you much room for water. I would also run the skimmer in the sump if at all possible. I think you may lose some of the critters you are trying to culture by having the skimmer running in the fuge. You could sit the skimmer beside the sump with the PH
in the sump...sort of run it external...if you have room for that. You might have to extend the hose from the PH
to the skimmer to do that though.
, drill the fuge for at least a 1" drain and use a Maxi Jet 900/1200 to supply the water to it. I think that will give you the best results with the least danger of a spill.