I built my manifold so it goes all the way around the top of the tank.  Then I have lots of outlets.  Most of them are capped off, and 4 of them have locline.  I have one from each direction, but if I had a bigger tank I think I would make all the outlets on the front of the tank pushing towards the back.

Adam

Sorry to revive a dead thread, but I'm about to get parts to put a closed loop together but I'm not completely sure how to do it. How does it look to have diffusers in the front of the tank? Would it look better to only have them coming out on the back and sides?

Pistonfisher, do you happen to have any pics of your system yet?

Bruce-
So can you tell us about it?  Did it work out for you?  I'm struggling with mine.

Adam

'm trying to figure out if this would work for my closed loop outputs. The left side is a 90 degree tee for surface agitation and general water movement. The right side the tee is for countercurrent (maybe) and the elbow would move water behind the rocks.  The plumbing itself is going to be mag5, SQWD, and 3/4" PVC. The tank is also only 18 gallons. Here is a bad drawing:

Just to let everyone know...placing a 't' inline with a rio 2100 (692 gph) doesn't work!  I place one 't' before my 90 and noticed the flow out the 90 barely chanced! but the flow out the 't' was barely noticeable.  To solve this you may need to use a 't' with an endcap to create backpressure to increase flow out of both, but I don't really believe it would work well.

Using smaller pvc will actually decrease your flow and create backpressure on your mag5.  Using larger pvc decreases viscostiy (resistance to flow) so, more water will actually flow and it will be less hard on your pump.  (this isn't hard fact just what I have been told and read).

This project is so easy and cheap that you can get both sizes and try it out.  Someone on the message board may even have extra pvc/ fittings.  I have some 3/4 't's you can have

John

Thanks for everybody's answers. Still haven't decided if I'm going to go with 3/4 or 1/2 pvc yet

jglover how did you connect the locline to your sqwd?

3/4 inch pvc works great!  When tied up against the plastic crown of the tank it's hardly noticeable.  The thing that I think was great was that the internal pressure of a Rio 2100 isn't great enough to cause a major leak (all my plumping is internal), so I didn't need to seal the pvc!  So I can continually take the system apart and replace with different fittings to see what works best.

John