[cxjoshuax21x]

So right now i only have a freshwater planted but im currently in the process of starting a 55 reef.now heres the thing i know alot about saltwater fish and corals.i run a fish department in a exotic pet store.im ganna get a sump and already have an hob oveflow box.but the problem is i dont know how to match the input of the over flow (300 gph) to the output.i cant find a pump that 300 gph!there all a little over or under.any ideas?

 

[Invic]

Ball valve on the return also remember head pressure aka pump height will drastically change gph. Always have a valve to dial things in. Pump ratings are always off so you never know what gph it's giving out.

 

[dirtycontour]

+1, here is a calculator.
http://www.reefcentral.com/calc/hlc2.php