Closed Loop w/ SQWD on 180 Reef

[macdo1sl]

Hello everyone,

I realize this subject is discussed frequently, but I have some specific questions that will help me out tremendously. First off, I am moving my 180 gallon acrylic (soon-to-be reef) tank in a month. I am looking to increase circulation. I currently own a mag-drive 1800 that is running as the main pump which is connected to the filter setup.

Here is my closed loop plan:
1.) drill two 1.5" holes to accomidate two 1" bulkheads near the bottom center of the tank, behind the rock-work. These will be the pump intakes and will have those plastic filter things on them.
2.) drill two or four 1" holes near the top to accomidate the pumps return. I can't decide how many I should use. Any advice for a 180 (72" x 24" x 24")? 4 returns would spread out the flow better and I could use 2 SQWDs.
3.) Use 1-2 SQWD depending on the configuration. Would 2 be overkill? Since they only handle 1400 gph, I will be wasting a Mag-Drive 1800. With only 1 SQWD, I'd need to plumb part of the flow somewhere else. So either another SQWD or another return.
4.) By a Mag-Drive 1200 pump to replace my Mag-Drive 1800 for the main filter return. I am thinking that the 1800 is better for circulation purposes on a closed-loop becuase it has a higher flow rate. Currently it is plumbed to a 3/4" return which has quite a few bends before it reaches the tank. The thought that I have is that it is working too hard for this and I am not getting optimal flow from it. A 1200 should work better. Your thoughts are appreciated...

Thanks for helping me,
Scott

[macdo1sl]

Also,

How high would you recommend the return holes be drilled above the bottom of the tank? 6"?

Thanks.

[wetworx101]

You are in the right direction...just need a couple tweaks.

1. SCWDs switching rate is dependant on the input flow. If you run 1800 gph through it it will likely break, and even if you were to reduce the flow to just under 1400gph, your flow is going to switch faster than christmas lights! You will want to split the pump outputs into two SCWDs. Now here is the fun part (optional)...only run three ports into the tank for returns. Have the SCWDs each run to an outside return, but for the center return, combine them together again. One of the SCWDs will switch faster then the other, and at random, they will both cut off, and then both come on at double speed...and then spend some time with it being on constantly. Just a fun thing to do when you have two SCWDs. You could even just split the SCWDs before them & after the pump, and recombine their outputs and just flow into just 2 ports...but then you ramdomly end up with more times where both are on at once...reducing the wave effect...but the three outlets...very cool effect. The side outlets switch on/off like normal, but the center one gets really crazy...

2. On another note, I wouldnt place your intakes so low. Since you will no doubt have intake screens/strainers on these intakes, critters and crd will build up on these areas. I place my intakes for closed loops further up. This allows you to see the intakes easier and not have such a hard time when having to reach in and clean them. I try to make the intakes around 6" from the surface.

3. There is a 1.5" SCWD slated for release later this year. This would of course naturally accomidate your size tank better. If you are going to take your time in setting this up anyways...just wait and see...it should be out in fall.

[macdo1sl]

Thanks wetworx101,

I really like your idea for using 3 returns. You said 6" from the surface for the intakes. I really don't want them to be visible and I'd like them to be behind the rocks. How about 9" from the bottom?

[wetworx101]

Sure, its all good. The idea is to just keep them off the bottom so they are easier to clean off, more visible to check on, and keeping them farther from the bottom will prevent crap from collecting on them as well.

You like that 3 return idea, eh? I thought it was pretty trick when I thought about it too.