JEB
I'm assuming you have this pump as a return for a wet/dry or sump ?
Or are you just using it as a powerhead to circulate water ?
I've got a Cap 1800
The box flow chart shows the following rates;
425 gph @ 3 feet head
325 gph @ 4 feet head
I've use it to mix saltwater, and as a backup for my 30 gallon tank return pump.
I think it is way under rated for use as a return pump on a 75 gallon tank too.
If this is your case then you must also consider the rating on your overflow.
You need to really know the overflow rating prior to switching out pumps.
Then you can make a wise decision.
You may find you need to upgrade the overflow as well, or you may be okay, and just need a bigger pump.
Until then ..... it's all just guessing and that can get messy.
