Sand getting sucked into overflow

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rgeorge3

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I just set up a 180 gal tank and I'm having a strange issue - I keep getting sand down in my sump. It looks like the upflow slots for the internal overflow are sucking sand up from the bottom and dumping it into the overflow. Some of this sand is making its way into the drain and ending up in the rollermat/sump. I initially thought that maybe I just accidentally spilled some sand in the overflow when adding the sand but I pumped the sand out and its coming back.

I tried to pull the sand away from the slots but that's not helping so far and wouldn't be a long term solution given fish like diamond gobies that move sand wherever they feel like and the sand drifting from the powerhead flow. You can see the flow being generated at these slots and sand flickering around at the openings so that has to be what's causing it. I need to find another alternative to stop this from happening but I'm at a loss.

My other tank barely has any flow through the upflow slots but this one seems to have so much that its able to lift sand up the 2 feet to make it into the overflow.

Anyone have an issue like this before or have any ideas on how to stop the sand from getting sucked up and into the overflow?
 
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rgeorge3

rgeorge3

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Here’s a video and some pics. This sand accumulated in the span of about 3 hours.

E0DB1658-5400-4573-8250-80598CCC2ABE.jpeg
7935E1ED-73EA-412E-AC63-39C2FD398E41.jpeg



 
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rgeorge3

rgeorge3

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The sand is the caribsea special grade so it’s not like it’s a fine grain sand. The flow is a Vortech L2 running at around 35% so maybe 6x turnover in the tank. Is that enough flow to pull that large of a particle size up through an up flow?
 
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rgeorge3

rgeorge3

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All I see is the flow pulling up from the lower weir types slots in the internal overflow. The overflow is double walled with a glass box silicones to the tank and an acrylic outer shell with the wier teeth cut in the top and slots at the bottom to produce the up flow into the overflow. That upflow seems to be where it’s pulling the sand from but that flow isn’t typically that strong.
 
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rgeorge3

rgeorge3

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Just to test I turned the L2 down to around 25% (I didn’t update it to Mobius so I’m not 100% sure on the percentage. It has 3 lights lit on the controller) and slid some sand up to the slots and it immediately started pulling the sand up and into the overflow. That flow should only be around 4x turnover so it seems like it’s happening regardless of the flow.
 
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rgeorge3

rgeorge3

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The tank is a SCA 180. They are local to me here in SoCal and they work with my wife occasionally so I got a great deal on it. Its crazy to think that the flow through the walls of the overflow would be so strong I would have to worry about sand getting sucked in...

I searched for other issues like this and came up with nothing so hopefully someone has an idea that can fix it. I reached out to the manufacturer but I'm waiting on a response.

I guess in the grand scheme of things, I could just silicone that closed and not utilize the lower weirs. However, if they are pulling that much water from the lower part of the tank, I wouldn't think its a bad thing to have.
 
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rgeorge3

rgeorge3

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So it looks like the sand is starting to subside a bit… I have no idea why though. All I can think about is maybe a film is building up in between the inner and outer overflows and it’s causing the sand to slow just enough to not go over the edge or enough heavier particles have filled the gap and slowed the flow down a bit.

In total about half a cup of sand went through and that was just in 5 days. Thankfully it stopped because if it didn’t, that thing would have filled in no time.

Thanks for the suggestions on how to address the issue.
 
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