If you are strictly talking about flow rates through your sump, than only the amount your skimmer is rated for is needed. I guess if you use filter socks have some additional flow won't be a waste as it will get filtered via the sock, but not the skimmer. I don't think it is a bad thing to have a higher flow rate through your sump, but it isn't necessary and is more likely to cause micro bubbles. The other con to have higher flow rates through the sump is the potential of pumping faster than your drains can handle. Flow inside the tank should come from powerheads or a closed loop, unless your tank is small enough that just the return pump alone is enough. As for how much flow inside the tank you need will depend on the livestock you keep. Every coral needs enough flow to move the polyps, but some like SPS like a higher flow rate. I think just as with lighting we over do flow rate as well.Looking forward to this, as I've heard very wide range of opinion!
Most recently, one I had not heard before, match it to your skimmers capacity and use power heads for flow needs of the inhabitants.
Guessing most of us turn our tanks over way more than our skimmer rating!
Tagging along~
Tapa
I think your getting the rating confused with gph flow on the skimmer. Manufactures rate skimmers for a particular size tank (75g and 150g rating you said). The flow everyone is referring to is gph. What you do is find out how many gph your skimmer pump draws in and match that to your return pump. IMO less is better, my skimmer pulls about a 100gph more than my return pushes through my sump.So the confusing part to me about matching you skimmer is the number is often perceived as 'over rated' (i.e. Rated for 150g and folks use it on a 75g tank).
Should you be turning over 75gph, 150gph, or 450gph(6x)???
Fairly sure the majority of tanks I've seen are closer to 6x....and that the skimmer manufacturers warn about going 'too big' as to not have enough waste to precipitate out (i.e. An 10" barrel will struggle on a 75g to produce waste).
Hmm
Tapa