Livesand only filtration

[Cody Ray]

I have a similar thread running in Advanced topics however there are more aquarists in this section so hopfully there will be more responses here

Anyway I have been pondering the idea of using livesand, specifically an upside-down DSB, instead of liverock. It would run pretty much like a reverse undergravel filter with 1-4mm aragonite sand instead of crushed coral. A pump attached to an undergravel filter would push water thru the sand back up into the water column. A filter sponge would be attached to to the intake of the pump to prevent detritus or livestock from ending up under the sandbed.

For thoughs of you who have never heard of an upside-down sandbed here is a simple diagram of how it works:



With this design the sandbed recieves circulation from below and above the sand which provides more water to the bacteria within the sand. Denitrifying bacteria grow in the center of the sandbead. The corals grow on coral rubble to increase the total surface area and decrease dead spots. Encrusting corals would have larger rocks or possibly eggcrate. Unfortunatly this doesn't provide much in the way of cover for fish so I would have to wait until the coral growth provided enough hiding places for fish that are shyer. It would look similar to this only inside of an aquarium

[reefnetworth]

1-4mm is shallow, that converts to 0.03937-0.15748" 4-6 inches or 10-15mm, is considered DSB. i dont think it will work because the pump that would push flow through that deep of sand would blow it into a sandstorm or into the return. 1-4mm is not enough to filter a tank. REEF-ON!!!

[lux_06]

ok so why not suck water through the sand rather then pushing it back through, there will be less disturbance this way.

cheack out

http://www.garf.org/bulletproofreef/plenum.asp

just enter your tank details in that box thingy and check out the next page...

[labatt]

I'm no expert here so if i'm wrong very sorry.
Im assuming that you were talkinh about grain size in the 1-4mm. I think one of the main problems with this setup would be a lack of anaerobic??? zones to break down some bacteria (the name isn't coming to me). Part of the way LR works and a DSB is there are areas of low O2 toward the center of the rocks and deeper in the DSB that break down nitrites or trates (dont remember which) into nitrogen gas. You probably wouldn't get that with your setup.

Again, please smack me if I'm wrong. If someone could chime in and verify this or discredit it TYIA.

[lux_06]

yeh i do think that is important to the way a dsb works, after all those little bubbles of gas would never exist in a system like this, however sand would be a good filter and i feel that if you could pull a slow current through the area where the benficial bacteria grow it would provide satisfactory filtration.

it makes me wonder how the bacteria 2 inches under the sand even comes in contact with the flowing water, but it must somehow, you have to wonder though if providing those areas with more water flow are you giving the bacteria a better chance, however i agree that some aspects of the benefits from DSB filtration would disapeer.

[Cody Ray]

Originally posted by nano4brains
1-4mm is shallow, that converts to 0.03937-0.15748" 4-6 inches or 10-15mm, is considered DSB. i dont think it will work because the pump that would push flow through that deep of sand would blow it into a sandstorm or into the return. 1-4mm is not enough to filter a tank. REEF-ON!!!

Im sorry I wasn't clear enough I was refering to grain size not depth.

The reason for an upside-down sandbed is that it helps prevent detritus from building up in the sand. I believe there was an article in the 2005 issue of Marine and Reef but I can't find mine. It also provides the bacteria within the sand a faster supply of ammonia, which in turn is supposed to speed up the nitrification process. You still have denitrifying bacteria but they occur in the middle to upper portion of the sandbed as the flow has been reversed. Then the upper most section of the sandbed is filled with nitrifying bacteria because it is exposed to the water column itself. By running a sandbed this way you also prevent sulfate from building up within the sand.

Edit:

Here is the name of the article in question

Sump Improvement
For starters, consider an upside-down sand bed.
By Dr. Charles Matthews

[reefnewbie54321]

I have read an article in FAMA I believe about the use of an upside down sand bed but its purpose was not for filtration but rather a constant source of calcium for a low-demanding tank.

Interested in seeing some more responses

[Cody Ray]

Well I do plan on using it for an sps system so anything that would help with calcium depletion is an added bonus!

[reefnewbie54321]

Okay I did some reading and found a cool thread that discussed a RFUGF Reverse Flow Under Gravel Filter which is the same idea as an upside down DSB. The main issue is sand is so constricting and water would not be able pass through it evenly and instead you would create channeling where water would burst through holes at the surface. There is a meber here PualB that has run an RFUGF for 35 years but he uses dolamite as a substrate so its less contricting and gets a more even flow. To get an even flow the sna d cant be contricting and without the sand being constricting bacteria will not grow. It will grow it the various clogs that form within the bed from detrius but it wont compare to the type of filtration a DSB can provide. It would be more stable in the long run but you pretty much loose the whole DSB concept when a RFUGF is added. You also mentioned that detrius would not settle on the sand bed and I find this unrealistic becuase for the bed to get an even flow it would have to be run extremly slow and there for detrius woukd accumulate just as it would on a DSB.

[Cody Ray]

Would you mind posting a link to this?

[oralsturgeon]

The sand would have to sit on some type of membrane to prevent the sand from flowing through the pumb back in to the main display tank... Interesting Idea, not sure how it would work

[reefnewbie54321]

Its from another site so I dont think I should post it ... I tried to PM you but your mailbox was full. Empty it out and I'll send it to you.

Its on Reef Frontiers in advance topics on the 1st page

[Cody Ray]

Ok empty

[DamnDamsel]

You will be oxegenating the sand bed. It will no longer remove Nitrate. To remove Nitrate you must create an anaerobic(sp) enviroment. With no O2 to survive off of the bacteria are pulling another available element out of the Nitrate. This breaks down the Nitrate ant that is the bubbles you see rise from the DSB once in awhile.

If you run airated water through your sand you will need to find another Nitrate export.

PS You may already know this just did not get that impression from your post.

[Cody Ray]

Just because water is running through the bed doesn't mean anaerobic conditions will not occur. Aerobic bacteria will still use oxygen so there will be a section that recieves little to no O2.

[DamnDamsel]

I would not have thought it possible for teh aerobic bact to work fast enough to do that. How slow is the flow going to be?

[Cody Ray]

between 20-40 gph in a 20 gallon. The sand would be roughly 6" deep.

[Ursus]

So basically this will be a remote DSB? Or is the DSB in the tank itself?

[reefnewbie54321]

Originally posted by Ursus
So basically this will be a remote DSB? Or is the DSB in the tank itself?

I beleiev he wants to use a RFUGF with 6 inches of sand on top and run it very low flow in the main display. RFUGF were used before wet/drys became populor but were used with crushed coral. Its hard to say if it will work with sand becuase it is so dense and might just create pockets were the flow burts through instead of an even flow. I am also not so sure on were low-oxygen pockets would form.

ChinChek YGPM

[Cody Ray]

Got PM, but u must be a member to view the thread. This has been done before by Charles Matthews, however the only difference was that he used liverock in his display as well. I guess this would prove whether it actually works or that his liverock was processing the nitrate produced my his setup.

Edit: I found a picture of his setup in a latter issue of Marine and Reef USA, he actually uses a layer of crushed coral, window screen, and then sand.