is 1400 GPH too much for a 75 gallon tank? i wanted to know because i can get a CHEAP overflow on ---- and i want my only water movement supply to be with locline (on return of sump)
I would say that it depends on what kind of corals you want to be able to keep, but probably not. That is slightly less than 20x turnover so it shouldn't be too strong for very many things.
with my wave make my 75g tank cycles between 35x and 55x turnover rate (maybe a little more).
I think your going to find that your not going to have enough flow with only one source of flow you'll have a lot of flow in one general area and almost completly dead spots on the other side of the tank.
You will need more flow. I wouldnt even include the return from the sump in your expectations of flow in your tank,its sort of like a bonus. At minimum you will need a couple of Koralia 3's, you may get away with something smaller if you are keeping softys but you run the risk of dead spots in your tank that are basically a ticking timebomb.