Pump For 38 Gallon Hooked Up To SCWD

[manny]

What size pump should I have for my 38 gallon tank? It's gonna be hooked up to a scwd and will be at the same height as my tank which is 20 inches tall. Think a Mag 5 will work or should I go higher?

Oh yeah, its gonna be in a closed loop

[kaiser]

Go with mag 7. the scwd reduces the flow by about 20%

[manny]

I'm going mostly sps and was told that the 9.5 and higher would add alot more heat to my tank running it externally. So I'm pretty much limited to the 7 unless I can stick the 9.5 in a cool tank of water behind the tank or somethin. Maybe an Eheim?

[Tim Marvin]

Mag 9 or 12. Externally won't add much heat... Internally might add a little. Put a fan on them if you are worried about heat.

[oceancube]

hey manny well thought i would add my experince with a mag 9.5 externally, well your tank will go up in heat about 2 degrees as mine did, i then put it in the sump and it did a little better, i think those mags 9 or higher run hot externally and internally, just my 2 cent's, i would do a mag7 in that tank you have and ditch the sqwd, you will loss tons of flow with that junk, trust me i tried it twice with no luck not even a mag 9.5 did it on my 58 with two outlets on the closed loop, your corals will not know the difference between regular flow and switching flow, it's all the same ,as long as there's flow in the tank period!you will also not hear that darn grinding sound it makes! you can call me if you need help too dude!!

[manny]

Thanks for the input guys. When I got the scwd I didn't take into consideration the splitting of it was gonna cut down on the o/p from each return. I've read that when it switches, it doesn't completely shut down the other side. So in calculating GPH coming out of each side would you calculate the regular loss of flow do to 90 degree turns and such and then after figuring that out, then figure the loss of flow that's gonna happen from the scwd using a chart like what was posted in Vendor and Procuct Experiences under "SCWD" and then multiply that number by like 30% and 60% to find out how much would be coming from each return pipe?? I'm just asking so that any other people who read this post will be able to know this stuff before they purchase one of these.

[malofish]

If you need a mag7 I just bought one about 4 days ago and was not too happy, I just bought a mag9.5 for my tank! but then again I havea 54 bowfront. P.M. me if your interested.

[matt]

It makes absolutely no sense that the mag would heat up your tank more running externally. If it's in the tank water, ALL the cooling is done by the water. If it's external, maybe the pump will heat up more, but the air will be doing some of the cooling. At least that's what makes sense. Maybe I'm missing something.

Anyhow, Manny, why don't get a decent external pump like an iwaki or a pan world/blueline HD? You'll be much happier over the long run, I bet. It'll last forever, run cool, and never lose much flow. For the sqwd, I guess a pressure rated pump would be right to minimize flow loss. I ran an iwaki 20rxt n my 45 and was very happy with it.

[manny]

JJ, I'll let you know if I'm gonna be needing that Mag7.


It makes absolutely no sense that the mag would heat up your tank more running externally. If it's in the tank water, ALL the cooling is done by the water. If it's external, maybe the pump will heat up more, but the air will be doing some of the cooling. At least that's what makes sense. Maybe I'm missing something.
Matt, I guess I can see how it would heat it up. It would act kinda the opposite way a chiller works and heat up the water as it passes through the pump. At least that's all I can think of. I dunno. As for going with an Iwaki, that would be best but I don't think I could afford it right now. I'm already gonna be running a MD20RLT from my sump and that's gonna be hooked up to a scwd. Maybe I could find a good deal on one and do that instead or I may just scrap the whole sqwd idea all together.

Do they really make that grindin noise when you use the pump on em? I've heard it before after blowing through them but thought the water passing through it would quiet it down.