Your right these 2 pumps make different noise, one is noisier than the other.

Make sure the spacer is on the correct thickness and that they're aligned. They barely make any noise.

And on the spacer, make sure the little nibs go into the holes and don't get bent

Not sure if you have made a decision yet. Here is a link on a comparison of measured flow output for propeller pumps.

I have both a MP40 and a Tunze 6305(x2) and prefer the Tunze because of their maneuverability.

http://www.advancedaquarist.com/2011/7/aafeature

Note the experiment was sponsored in part by Ecotech.

HTH

Lots of scientific bla bla bla to me.:lol: Although I did see the charts. I don't think the tunze pump flow rates would be that much lower than the advertised rates, this seems a little biased.

Again, I think a big thing about Vortech is their ability to create the flows and undertows, therefore the ability to point them is irrevelant.

All are good products though, so whatever you choose, I think you will be happy.

Do a search on reef central and you will see the 6105s were putting out much less than advertised. The problem was an 18v power supply instead of the 24v. Now that the proper ones are out I have seen a couple reviews stating the 6105s can be heard outside the tank.

How much sand disruption do you think you'd have at the front of a tank if you had a 6 or 7 foot long tank, 36" wide front to back and 30" tall with vortech's running full out at the back of the tank?

I'm running ~85% power across 4' and there is no sand disruption except for directly under the pumps. Some minor changes in the sand but if I had it a 100% there would probably be no sand below the pumps.

With a 30" tall tank you'll be able to mount the VorTechs higher and there should be minimal sandbed disruption, if any. I think the top of my MP40s are about 3.5 inches from the water surface on a standard 24" inch tall 4 foot long 77 gal tank. I also run them at about 85%. If they were mounted any closer to the surface, they would probably be pulling little air tornados (vorteces) from the surface. You've got an extra 6 inches of height and 3 feet of distance to the other glass, so depending on the depth of your sandbed, you should be ok. The flow pattern of VorTechs broadens quickly as distance from the nozzle increases. Another reason the pointing issue as with other power heads is really a non issue.