River tank manifold questions

[Loaches4me]

I'm resurrecting my old 20long river tank and I started doing some thinking on a couple of things....

1) My original build was using 3/4" pvc pipe. Would there be any pros/cons to going to 1/2" pipe?
2) My intakes and powerheads are all the same height. Curious if it be advantageous to alternate the heights on the powerheads and the intakes?

I found some nice Hillis and I just had to set this tank back up.

If anyone wants to weigh in on this, that would be greatly appreciated.

[Jim Powers]

The nice thing about the river tank manifold as designed by Martin Thoene, is that it is very flexible. Many on this site have altered it to their needs with great success.
I really can't answer your first question. I imagine it would make some difference in the fact that the larger pipe can carry a larger volume of water at any given time.
As for the second question, it might be more like a natural stream flow to have the current at all levels of the tank but it might depend on what dither fish you put in the tank (if any) and how much current they like.

[Diana]

1/2" pipe is fine for a 20 long, and even larger. 1/2" pvc can move a LOT of water. As the pumps approach 3-400 gph, then you might want to increase the size to 3/4".

PVC is cheap. Try setting it up with higher and lower intakes and outlets. See what happens. If you do not like it you can always cut the pipe shorter, or add some more to make it higher.

A 20 long is so shallow that I do not see any real difference with higher or lower intakes and outlets. It might mean something in a taller tank. Do not put the inlet so low that it gets plugged with substrate. I would keep them about mid-tank (on a 20 long). Similarly, if you are using a powerhead for the outlet, some seem to quit if the water level drops just a bit and they are exposed to the air, even a little bit. If you are using a canister filter then you can adjust the intake and outlet however you want, of course.

[Loaches4me]

my existing one, both the intakes and outputs are midway up. I angle the out flow away from the intakes a bit. I was just curious if any of the things I mentioned would have any possitive impact. I pickup my Hilli's this week.

[Jim Powers]

What species of hillstreams are you buying ?