first, i want to buy a pair of Hydor Koralia's, but not sure to buy #3 or #4? i plan to get some softies later on down the road, but is 1200 GPH X 2 alot of flow?? i onbly have a pair of maxi-jet 1200's, my second question is that i want to buy a skimmer but i dont have a sump, i only have a wet/dry canister filter so i would need one that hangs on the back but i only have a limited amout of space cause i have 2 light fixtures and covers most of the top of tank, i probably have like 4-5 inches of space in the back, or maybe put it under the tank but i really want it as easy as possible, oh yeah i have a 72 gallon tank with some live rock and sand (i think its alive), Thanks