|
If your drain or overflow line is 1" then you should be fine but the size and the height of the prefilter can also be a limiting factor. 900 GPH is not a lot for even small tanks so I suspect you should be fine. You could put a valve in between the pump and the tank and throttle it back a bit untill you can observe the performance more closely. However you should know within minutes if it is ok. It will either be fine or it will start to get too close to the top of your tank right away.It won't change overnight. Most tanks with high return flow see the water level a couple cm (@1/2") above the prefilter edge. Also make sure that the water is not being restricted by dirty prefilter floss or poorly designed standpipe etc.
Just keep in mind that you always place valves on the discharge end of the pump and not the suction side.
PVC wont help and in fact are less efficient than flexible pipes as long as your comparing the same ID. Clear flex tubing can get restricted with algae over time though. White PVC "spaflex" is ideal in that it is flexible, mates with standard PVC fittings and will not grow algae due to light penetration.
Don't get the smaller pump unless you absolutely have to. You'll be sorry later on. In fact if your tank is designed for a max flow of 700 GPH it is hardly what I would call reef ready.
|