River manifold problem

[furkz]

Hello there

I've built my first manifold maybe about a week ago, its cycling at the moment. Im planning to stock it with some loaches.

I've noticed I got a weird water flow and I think thats due my intake flow being low.

What do you guys think? How should I fix it to get it to be a unidirectional flow?

I will post some photos and a video below as well as the tanks specs.

SPECS
- 100x50x30 cm shallow tank about 150 liters
- Manifold built with 32mm pipes
- 2x 1000 L/H powerheads
- 2x Big sponges from a sponge filter





CURRENT FLOW



FLOW VIDEO
https://youtu.be/L8RZ2bbgQBk

Also could it be my intake set up?
my drilled pipe only fills de sponge half the way



Im open to all suggestions
Thank you so much for reading

[NancyD]

I'm no expert on manifold systems but you pics don't show. Can you try again please?

[Martin Thoene]

First time looking in here in years, so I'd better answer this one while I'm here.

Your tank isn't hugely long and ideally the pipe inside the sponge should reach to around a centimeter from the top of the sponge and be drilled so there as many holes as you can get in it, but stopping around 1cm from the bottom of the sponge. This allows the maximum amount of the sponge to pull water through it (good for mechanical and biological filtration).

The shorter the tank, the more chance of "bounce back" of pressurized water from the intake end. You'll always get more flow reversals the shorter the tank is. There are certain back flows in a natural river caused by low pressure areas created with water flow round rocks. Anything the water flows around will disrupt flow.

One thing to remember in an aquarium environment is that our water movement is created by a concentrated flow out of the powerheads rather than the entire volume of water moving in one direction like in a river. In your case, it's like two pressure waves moving down the tank through water that's not moving, so you get a disturbance in the flow because of that, then from your rocks.............then there's a bit of a bounce back effect of the intake end wall. It's an imperfect science.

Theoretically, if the flow potential of the intake was larger than what the powerheads pump (i.e. over 200 l/hr) PLUS the flow potential of the manifold exceeding 200 l/hr, then you might get a true one way flow, but I suspect there would still be the possibility of some flow reversal.

Martin.

[Bas Pels]

While we want to heve an unidirectional flow in a rivertank, remember that in a real river the flow is not really inidirectional. Every rock, tree or curve the river itself makes will cause turbulence in the water.

Riverine fish can cope with that.

[redshark1]

Yes, I just watched the flow in a river at the weekend. I actually saw that the flow moved upstream in part of the river! There were also low flow areas where the fish could congregate.