DSB - down through or upwelling

[aquariumdebacle]

OK, I am looking for specific advice on whether I should run my sand bed by pulling water down through it and flushing it once a month or should I have the water upwelling through it and still flushing monthly? I plan to just tricle the water though either way to keep it anaerobic but I am not shure which way yo have the genarl flow.

 

[dnjan]

I would say that down through will do a better job of keeping anerobic anerobic. Assuming that the oxygen is taken out as the water works its way down.

However, I'm not saying that creating a bit of an inverted sand bed would not be a good thing. If you went from bottom up, and had a deep-enough sand bed, you would have the anerobic zone in the middle. Get it balanced (flow-wise) correctly, and it seems like you would have twice the sand-bed-area effectiveness.

 

[aquariumdebacle]

Thanks Don! I was actually thinking of keeping the entire bed anaerobic by either running a very slow flow (one turnover per week) or by running the water through a long tube to make sure it is anaerobic before it gets to the bed. I think I would have less clogging (provided I micro-filter the water) by going up through the sand bed. On the counter point to that stratedgy is that the ammonia will be produced above the bed and it would be a natural progression to have the water flow down throught the bed. In either case I will have a reverse flush of the bed once every month or two. I am trying to plan my system so that it will be easy to switch between the two ideals to see how low I can keep nitrates utilizing most of the sand bed and cycling the water through creating a large de-nitrator.

 

[dnjan]

Could you clarify how the long tube will remove oxygen from the water? Do you mean that the nutrients already in the will take up all available oxygen?

 

[aquariumdebacle]

Yes, that is what I am considering: a coiled 100ft. length of 1/2" tubing before it gets to the sand bed. I of course would not need that if it was to be a "down-through" strategy.

 

[aquariumdebacle]

I could really use some input on this issue! I am leaning towards upwelling but I still think it might be more effective if the water is drawn down through the substrate. Help me out let me know even if it's just an opinion

 

[aquariumdebacle]

Come on People! Not everyone has given up on the deep sand bed have they? where are the true believers?

 

[Scooterman]

Sounds like your utilizing a plenum of some sorts to do this flushing, have any sketches or drawings?

 

[dnjan]

Come on People! Not everyone has given up on the deep sand bed have they? where are the true believers?

Same deep bed for over 6 years now.

So, refresh my memory. Exactly what are you expecting to accomplish with the flushing? Since a deep sandbed naturally accumulates partially-decomposed organics, where will you be flushing these organics to?

Back into the tank (IMO) would not be good. So that rules out the reverse (bottom-up) flush. So if you are going to flush directly to someplace that can "process" the effluent, it has to be top-down. And then do you go to a refugium? Carbon and phosphate absorber canisters? Skimmer?

 

[aquariumdebacle]

The sand bed is not new but has been in bucket for a year. It is not accumulating organics and was very clean when I removed it from the main tank. I was thinking the upwelling could go up over the overflow if it did not cause too much disturbance. If done on a regular basis turning the bed aerobic for a few hours should not be detrimental. If I go for the down through strategy I can just flush it out of the system as part of a water change and it would cause the bed to go aerobic only for a few minutes. I have a .1 micron screen for the pleneum which covers most of the bottom. There will be some sand under the plenum and they will be covered by at least three or four inches of sand.

 

[dnjan]

So you are preventing particulates from getting to the sandbed, and it will only be processing disolved wastes? What do you expect to be flushing out?

 

[aquariumdebacle]

The screen is to prevent the fine sand from entering the plenums.

 

[Elmo18]

Hi Dan. I'm a sandbed guy, but not a plenum guy....so I'm not really sure what you're talking about upwelling, etc etc.

Can we at least get some pics of the situation? Of your tank?

Best,
Ilham

 

[MikeS]

With my experience with DSB's (5 years)and BB tank (14 months)...I'd say the best way to approch it is either a larger grain sand (2-5 mm) and plently of flow over the surface of the sandbed...and/or a plenum under it that can periodically be drawn off of... equaly important, I'd advice any DSB tank keeper to practice very agressive nutrient removal via skimming, water changes, carbon, ect...the lower the amount of nutrients and crud your DSB sinks, the better it will perform and the longer it will last...

MikeS

 

[aquariumdebacle]

Mike, I fully concur on the nutrient removal but I recommend that for all systems. What I am strategically looking for here is nitrate removal. I do have a 55 gallon tank that I can (and will plumb to - not sure if I will plumb directly or through the filter system, thanks Matt!) for some nutrient removal with an algae scrubber. I also have a skimmer with the possiblity of adding a home-made skimmer in the future. What I am looking for is a new approach to a deep sand bed that will at least prolong if not extend indefinitely the life of the sand bed. I am looking to answer specifically the problem of nutrient accumulation in a sand bed.

With a draw down system I can export the products of a sand bed to a phosphate filter or export entirely by removal. The main problem I see with that is the continued accumulation of organics in the sand bed. Over time, this may clog the fine mesh of the plenum or even the sand bed itself. I think that by reverse flushing this design I can forstall the sand bed replacement but maybe not eliminate the problem entirely.

With an upwelling system I believe I will be able to keep the sandbed clean indefintely as long as I keep materials (by microfiltering) from entering the plenum directly and clogging the mesh from the inside. This would mean that only disolved organics would be broken down in the sandbed thereby negating my trickle filter nitrate factory which I refuse to eliminate from this system due to its greatly enhanced outgassing capabilities.

Thanks for the input everybody! I need to really think this through before I plumb the system. Ideally I would like to incorporate both options and may be even both by running one side one way and the other differently and see which way removes the most material and stays stable over time.

 

[aquariumdebacle]

going to get a beer but will check back later

 

[jsmkmavity]

the one problem i see is when you establish a dsb it becomes filled with different bacteria in amounts that form equilibrium in the system (biological filter) due to aerobic areas and anaerobic areas. this whole system would be disrupted and thrown out of balance every time you back flush it which could cause nitrate, nitrite, or amminia spikes and would take time to settle back to equilibrium similar to setting up a new tank. the only way i see to avoid that broblem is to have separate sections in the dsb so you dont disturb the whole thing when you back flush, only a small section at a time like 1/4 or less.

 

[aquariumdebacle]

Yes, I understand this concept and realize that this is a traditional thinking. Most bacteria in our systems are incredibly resistant and are what are called faulcative aerobic/anaerobic bacteria which means they prefer one or the other, O2 or not to O2.

What I inherently believe is that these populations can withstand considerable short term change. Causing an anaerobic bed to go aerobic for a few minutes or even a few hours is not going to cause the system to crash. Now if there are people with the opinion out there that I am totally off base, I want to here from you and I want good reasons to the effect that I could cause detrimental damage to the system. I want to know that I am at least thinking about the possibilties. let me hear you roar!

 

[dnjan]

With an upwelling system I believe I will be able to keep the sandbed clean indefintely as long as I keep materials (by microfiltering) from entering the plenum directly and clogging the mesh from the inside. .

Just to clarify - you would only microfilter the water that you are forcing through the plenum, not all the water that goes into the remote sump where you have this sandbed, correct?

Personally, I think that with a remote sandbed, protected from particulates with a frequently-cleaned filter sock, life should be indefinite. The sandbed problems I am familiar with are caused by accumulated organic particulates in the sandbed.

So, just to complicate your experiment, you could also have a sandbed with no plenum, but protected with a filter sock or other mechanism to keep the organic particulates out of the sandbed.

 

[Scooterman]

It is so much easier to just remove all the detritus before it ever needs anymore processing that the LR & skimmer misses, way too easy. JMO