Jason,
I have a Reeflo Blackfin pump (2400gph) on an OM4 with 3 Revolution heads (discontinued I believe) on my 180g system. Here is the OM4 valve above and behind the tank, behind the lights, in the canopy that extends all the way off the tank to the wall.
And here is the external pump down at the right hand end of the stand.
Chris at Reeflo has been very helpful, and the pump works reliably (4 years now), but it makes a bit more noise than I want... and it gets louder by the month. I have had a seal leak and Reeflo did great work with taking care of it. They replaced the motor too as the original was pretty noisy after just 6 months. So I'm very happy with the customer service, but not totally happy with the pump. I have a used Dolphin pump I may try or I may just get a new DC12000 adjustable pump once they get the bugs worked out.
I got the OM4 used and after a bit of 'fixing' I put it to work and it has run flawlessly for 4 years. I've never even cleaned it. I run it 16 hours a day and shut it down for 8 hours overnight. I'd like to have it running at a reduced speed, but the Reeflow isn't built for that (thus why I want a DC12000 pump). The Revolution heads are very cool and really make for great random water flow, but they are a bit obtrusive sticking into the water from above. They have run perfectly and I'm only getting to the point of pulling them for their 2nd cleaning in 4 years of use.
And given an external pump, I decided to 'line' the inside of my stand with a flexible PVC shower pan liner (not an original idea by me, a friend had done it before I set my system up). I highly recommend it if you can incorporate it into your stand! You can get it at Home Depot in 3' and 4' widths and any length (it comes on huge bulk rolls). It isn't the prettiest thing in my stand, but when the pump started leaking it did it's job. It also protects the stand from any small spills. It also saved me from a major flood when a siphon break failed and 40 gallons of water siphoned down and overflowed the sump/refugium. I have a lot of spare room, but 20 gallons or so did overflow and the shower pan liner held it all. No leaks, no flood. I now have a drain at the very top of one end of the sump that should stop a sump overflow and it drains out of the stand and through an outside wall into the backyard. I also installed a bulkhead in the shower pan liner and ran it outside as well.
