I have an SPS dominant 80 gallon. I have 2 mp40’s, 1 mp10, and 2 gyre 330’s. The MP10 was from a 20 gallon tank that I shut down. I have a lot of flow for sure and is overkill if you are just starting a tank. However, you will find that the MP10 is not enough flow at all.
You should start with 2 mp40’s as a base, in my opinion. I had 1 MP10 and 1 mp40 for a while and that was not enough. A lot of this will depend on what coral you want to keep as well. Check your glass thickness as well. My MP10 barely stays on the glass because it is too thick. I have to use zip tie mounts to keep it in place.
From my experience it’s better to start with more than you think you need so you don’t buy a pump to find out 6 months later it’s not enough and have to rebuy something else, which I have done too many times. The MP40 will go pretty low on flow if you are worried about too much.
The biggest thing I worry about is keeping detritus off the bottom of my tank and it takes many pumps positioned all around the tank to make that happen in my experience. If I am doing that I know my coals are getting the flow they need as well.
