Uneven Water Flow on Algae Scrubber

[onano]

I am having trouble get an even uniform water flow across the screen of the algae scrubber I am building. Its an in sump unit for a 75G tank driven by an MJ900 using 1/2"pvc. I cut the slit on a table saw so its nice and straight. The issue is that the water flows heaviest on the far half of the screen (away from pump) leaving the side of the screen closest to the pump dry.

The screen in 5.75" wide and 13.5" long. I calculated flow as 204GPH on the MJ900.

What am I missing???

 

[Osteopth]

I found that I needed a wide slit to get flow past the screen. If your screen is a tight fit then cut a wider slit.


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[pskelton]

Don't calculate the flow measure it. I suspect you will find the MJ900 is seriously under powered.

 

[Floyd R Turbo]

You need 35 GPH per inch of screen width. So if your screen is 6" wide then your flow you figured that you need is right, but you're forgetting about head loss. That's part of it. Pics of your setup would help

 

[onano]

I measured the flow at 205gph and went with a 5.75" wide screen. Basically a cube setup. The flow is still geared toward the far side of the screen but I have had it up and running for 7 days and just did my first cleaning. Here is a pic of how it looked after 6 days.

 

[onano]

Wow..messed that up. I went with a 3 cube per day setup (36sq in.) 5.75 wide by 6.25 long.

Here is the growth after 6 days. The flow covers the screen but is stronger on the far side away from the pump.



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[Floyd R Turbo]

Looks good. Flow will even out a little as screen grows in. It might take time though. Even if it doesn't completely fill in, you still have 95% of the screen covered with algae so I wouldn't stress out about it LOL

 

[onano]

Here is a pic of the screen right before cleaning after the second 7 day cycle (cleaned 7 days prior as recommended).

How does the growth/color look (I am colorblind so I need some assistance in determining if it is coloring and maturing as it should.)

Lighting is 12 on 12 off. Screen is 36 cu in (3 cubes). Lighting is 48 watts total (2 x 24).

Thanks
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[Floyd R Turbo]

It looks like your slot might not be straight and even.

 

[onano]

I cut the slot on a table saw. It is perfectly straight and even but the flow does run at an angle towards the far side of the screen as mentioned in my earlier posts. The entire screen does get flow but it is more concentrated from the center to the far side.

Is what I am getting looking good from a production standpoint (color..etc)

Any thoughts on evening out the flow. The pump had 1/2 return so I used all 1/2 pvc.

 

[Floyd R Turbo]

You might try doing 3/4" PVC and plumbing, head loss increases with reducing pipe diameter, but the water column pressure does not change as you increase diameter. So there's no harm in going to larger diameter plumbing.

I think your growth looks OK, you've got a mixture of dark brown growth in the middle and a swath of green on the right and a smaller one on the left top corner. So it's probably still pulling nutrients down, but the screen appears to be filling in so give it another week before changing anything.

What really matters is what your tank looks like, and what N and P are testing at. You can build a scrubber that doesn't grow perfect, but does everything you need. So keep that in mind

 

[onano]

The tank looks great. N and P test at 0. I think the algae in the DT is soaking up the P. I have a fine covering of HA on the rocks that the cleanup crew keeps under control but I am not algae free. I have to clean the glass very 2-3 days to get the green powdery stuff off the glass.

Here is a pic from my iPhone.


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[MaLi]

Onano,

I am a big supporter of ATS as well and have one running for my 90g cube from the first day (they grew up together )
What pipe type did you use for your screen holder ? Mind that if you used lower schedule (thinner walls) under heat the slot tends to close up.

My ATS is 24" long (SM100 replica) and I gave up on side inlet. I tee-ed the screen support right in the middle and thickness of the tee-connector keeps the slot perfectly spaced. I can post some pictures if you want.

hope it helps,
MaLi

 

[onano]

I used schedule 40 (thicker stuff). I'd be interested in seeing pics of you ats. The center connector sounds interesting.

 

[tomservo]

+1 on trying larger pipe if you have it handy.. The flow velocity also decreases with larger pipe, and I expect that is part of the problem, the inertia of the water moving tends to make most of it want to flow out the end of the pipe.

Floyd: I've noticed that even with a straight slot, the screen may not be straight, what can you do about that?