return / closed loop questions

[supermarvin76]

I am planning a 20 gallon high, and want to keep costs to a minium. I have a Mag 7 left over that I am planning on using for the return pump. Here are the questions that I have:

 

1. I am thinking of making the return a PVC manifold going around the top of the tank with about 4 return nozzles. Does this make sesne to do. I think this will help taper the flow rate from the mag 7 while nicely distributing the flow.

 

2. I am going to build an external overflow. The calculator on the "home" page here states that I should make atleast 12.5" surface skimmer to accomidate 700gph. Can I make it 15" and still be ok?

 

3. I would like to not have any power heads in the tank. I plan on a closed loop with possible a Mag 3 or Mag 5. Possibley using a SCWD. What size plumbing and bulkheads should be used?

 

4. Something I always woundered about closed loops. The intake for the pump is fairly deep in the tank. What are the chances / what can be done about a shrimp or small fish being sucked onto the intake screen.

 

If you reply to a question, thank you inadvance

[evilc66]

1. You could, but by the time you account for head loss and frictional loss from all the 90 degree bends, it will be a trickle at the four nozzles.

 

2. That guide is a minimum. You are more than welcome to make it bigger. It just means it can handle more flow.

 

3. SCWDs require pumps that can generate pressure. Usually this will cut the flow rate down on most pumps quite a bit. I'd say a Mag3 is far too small, and a Mag5 is borderline. Some of it will also depend on how much flow you want in the tank. Figure the SCWD will cut your flow by 20%. You bulkhead sizes will depend on how much flow you want too.

 

4. Provided you use a full 360 screen, there shouldn't be any worry about critters getting stuck to it. There isn't enough suction at any given point to do any harm.

[Mr. Fosi]

I have a 4-port SCWD closed loop on my 20H.

 

I modded in larger threaded ports for all the connections and put a screw top on the SCWD. The powerplant is a QuietOne 3000 and it runs through 1/2" thin-wall PVC. Mine puts out quite enough flow through the four locline nozzles. It isn't blasting and it isn't a trickle. If you tried this with a Mag 5 or 3 you wouldn't get much flow though.

 

Of course, I also have a sump return in addition to the closed loop but that isn't much more than 100 gph max.

 

The only way to keep shrimp and such out of your intakes is to put a screen on them that keep them well away. The suction from the intake is only overpowering in the immediate vicinity so if you can keep them an inch away, it shouldn't be too much of a problem.

[supermarvin76]

Thank you. What set up with pumps would you recommend? I would like to have a good amount of flow with no powerheads in the display. At the same time though, I don't want too much flow that it will be disruptive to softies or LPS. I am mainly looking to keep LPS and Montipora.

 

As much info that you can provide, the better.

 

Thank you!

[Mr. Fosi]

Can you post a rough diagram of what the display/sump orientation will be?

 

My system is a moderate flow closed loop and a low flow sump. Head calculators indicate that I am getting between 700-750 gph out of my closed loop before the SCWD is added in. All told I would guess it is more like 650-700. My sump return is only about 100 gph. My softies don't have a problem with the flow and the locline makes it possible to have a lot of different flow patterns so detritus ends up in the sump and not in the display.

 

If you want more flow than that, you will have to increase pipe diameter, reduce sharp bends or get bigger pumps.

[supermarvin76]

The sump is still in the planning. I want the biggest fuge possible. I am going to build the stand for the tank, and make it extra deep from front to back. I want a big fuge, but don't know exactly the tank to use with these dimensions. I was thinking of "stacking" the fuge over the sump in the stand, but am not sure how to plumb that yet.

 

The PVC mainfold was just an idea that I got from one of Anthony Calfo's books. I don't have to do that.

 

Keep the flow ideas coming please...

[supermarvin76]

I think that I have "upgraded" my idea to a 29 gallon.