*sigh* i'm still kinda new to this, if you can could you explain both? i understand the concept of a sump but construction and stuff needed is a dark area for me
overflow unit is this http://www.cprusa.com/products/overflows.html
they hang on the back of your tank and the water is siphoned down to your sump.
bulkhead is having a hole drilled in the back upper area of your tank and the water automatically flows down into your sump. below is a drawing I made kinda showing a bulkhead way.
do you know what size sump you want to use, aka 10gal aquarium. Since you will have 300gph going into the sump, I would use a return pump that is atleast 500 to 600 gph to make up for having to push the water against gravity. I would say the RIO 1700 (642gph) would work. $27.00 http://www.aquadirect.com/catalog/pumps/taam.htm
It would just sit inside the sump, along with you skimmer, heater and such. Another thing I would do is attach a 100 micron bag http://www.aquaticeco.com/aquatic1v1/it ... temid=3434 to the hose coming from the overflow box. This bag will sit inside your sump and will act as a mecanical filtration.
I'd recommend a Lifereef overflow (www.lifereef.com) they use a U tube design which you'll find is a lot more reliable than one that uses a powerhead.
You'll need PVC pipe, fittings, valves (gate and ball), unions, PVC primer and cement, and of course a sump and a return pump.
You can have an acrylic sump built or DIY one, you can use a glass tank or a rubbermaid container. When selecting a return pump keep in mind the head pressure your pump must overcome in order to return water to your tank at the desired rate.
When choosing a sump try to get the largest one you can fit under your stand or where you put it.
For my 58 gallon tank I have a 50 gallon sump and a 10 gallon refugium.