Basically you need 1000gph to fire the beckett optimally. The backpressure from the beckett and misc skimmer plumbing causes head loss. Pressure rated pumps are better at firing the beckett because they stay near the 1000gph mark even when pushing through the beckett and plumbing. If you use a non pressure rated pump you need to go to something with a lot of flow so even after it's all said and done you are still around the 1000gph mark to fire the beckett.
My opinions on the pumps you listed:
So T3 isn't near 1000gph.. so I woulnd't bother. Especially since the price is high and the company no longer exsists.
Similiar opinion as with the T3. Even though with the T4 being 1200gph it is not pressure rated and you would not get maximum foam production from your beckett.
Mag 18, good choice. It's quiet and will fire the beckett nicley. I have run this pump/skimmer combo myself. Requires no sump drilling and can be run in-sump.
Mak 4 is the best pump really, unless you want to pump out the real bucks and buy and Iwaki. Mak is a cheap copy of Iwaki pumps and are pressure rated. Something like 1140gph at 4' head. Fires the beckett simmilarly to the Mag 18 but with finer bubbles because it's pressure rated and has a little more umpf to it. Although needs to be run external and is has a hum from the cooling fan. The noise is barable but it's there.
Well Shao, if that doesn't make sense don't blame me. It's 2:30 am and I just got back from Victoria.
