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UGF with Sand


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I've started to get fascinated with undergravel filters. But if my next tank project happens, I was planning on using Black Diamond Blasting Sand, and plants.  

Is there a way to make it work?  

 

I've read a few threads on here, and I saw a mention of putting something between the sand and filter. But would that eventually get clogged?   Or do you count on waste breaking down faster so it won't clog? 

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I think UGF work great!  I've used them extensively in the past (don't have any currently as I am a bit obsessed with sumps at the moment).  I have some pretty elaborate setups where UGF was the main show for nitrification.

That said, my one fail at it was with too fine of sand.  I knew it immediately.  There was no flow coming out of the lift tubes (I always filled to just under the tubes when doing initial fill and then water changes to make sure I was getting good flow).  With sand I think it was like trying to suck a thick milkshake through a straw.  It might have worked better with a powerhead, but mine were all air driven.  Just a cautionary tale from a failed sand-UGF combo.  I'm not saying it absolutely can't work.  Just that I didn't manage it.

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Posted (edited)

I read that you can put weed fabric between the filter and the sand.  That'll let the water flow, but not the sand (assuming it's not very fine).  That may even leave the bottom of the tank clean if you had to tear down. 

But I'm thinking even that may get clogged up by debris.  Does anyone have experience with this? 

Also, the benefit of UGF was to efficiently use the gravel as a bio filter. But with sand (or sand like) substrate, I'm not sure if it still has the same kind surface area as gravel, or the ability to let the water flow through it. 

Edited by Gideyon
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I've never tried it, but I would think that a weed fabric and sand combo would ultimately fail with an air driven UGF, or at least cause additional maintenance issues.

I have always used UGFs with powerheads and gravel because unlike air, you actually know about how much water is moving through the gravel.  I have found nicks in the impellers indicating that a tiny piece of gravel will occasionally make it under the filter plate.  I would suspect that sand will get through more frequently.  My experience with outdoor gravel paths and weed fabric has shown that eventually the fabric will clog with roots and debris.  

Let us know how the blasting sand works.

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Yes, I've been considering that for a build I'm planning (custom tank and taking forever to get here!).  But because the tank would be for Rift Lake cichlids, I ultimately decided not to pursue it as I suspect their digging would result in anything that settled out being resuspended with multiple chances to make it through the overflow.

I think that it's decent idea for sand though!  Obviously it's pump driven and not air, but as long as the sand is course this could work.  An extreme flow version of water through a sand base is what pool filters do after all. 

I still suspect the sand would need to be fairly course, #20 screen or larger, or the water would form channels over time as the path of least resistance.  And if the tank is planted it might be best to stick to epiphytes like anubias and java fern.  Then there would be no concern about roots clogging.  I can imagine an Amazon sword clogging any UGF in short order.

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