No, you use a pump to push water from the sump up to the display. Then the drain just uses gravity to get the water back down to the sump. The size of your drain pipes and the height of the tank pretty much determines your pump choice
I havent set it up yet. I would say about 24" at leased.
Also should i encoraouge (sp) algea to grow in there?
Should i have a DSB and things like that?
No, not at all. Most of those flubal pumps can re-circulate water but cant push it up. Look for a pump with a maximum head presure in the range of 6-10 feet.
pretty sure you UK guys can get a hold of Eheim 1250 pumps. I'd prefer something like a Danner Mag 5 or 7 but from what I'm told you guys dont get those very often.