DSB Question

[Glenn]

If I set up a 20L and use a DSB of the recomended 4" then that only leaves 8" of tank depth. Is 4" really necessary? Or can I use a real fine sand to get the same effect with less depth? I know the purpose of a DSB is to create areas of low oxygen for bacterial purposes but does it have to be 4" to do this? If not can anyone recomend a grain size that would allow it to be a little more shallow? What abut South Down, is this small enough? Thanks in advance.

[tinyreef]

4" isn't necessary ime. some think it's mandatory others think it's detrimental. i suggest you try about 2", you can always add later little by little to go up 4" if you really want to.

 

the premise of a 4" minimum is popular but not necessary ime. i have sandbeds working at 1/4" to 3". the arguements for needing 4" just never seemed valid to me while everyone still espouses the same benefits derived from any size of live rock.

[Glenn]

Thanks tinyreef. Is there a maximum/recommended grain size for DSB's ?

[printerdown01]

I've heard 1-1.5" when using oolitic aragonite... other than that I don't really have any numbers for you... -sorry...

[tinyreef]

sorry if it sounded like a soapbox answer there.

 

i used to automatically think smaller the grains the better, i.e. sugar size, mud,

 

i'd suggest sugar to <1mm ~ 2mm granules. that's what works for me. i would recommend aragonite over silica, just mo though.

 

edit: oops, forgot the '<' sign there on 1mm

[Glenn]

Thanks you guys!

 

printerdown01: I was thinking of going with oolitic anyway, so that's great.

 

tinyreef: nah, I don't think you sounded soapboxy, just confident. Besides it's good to be passionate about this hobby. I like the idea of aragonite also (doesn't it help w/ pH and alkalinity?). About the guy with the big stones: That's what's so amazing about this hobby, if you know what you are doing your options are many.

 

Agian thanks for the help!

[Brianc_4]

It all depends on what you want to accomplish. Certainly, smaller grains of substrate provide more surface area for bacteria to grow. But, that is not the point of a DSB. The process which converts nitrates to nitrogen and oxygen, requires a very low oxygen enviornment(almost anaerobic). That is why live rock works. Its porous enough to provide that enviornment within the rock. It is the same thinking with a DSB, it takes about four inches of depth to provide a close to anaerobic enviornment. The real question is whether or not you need a DSB. And, the answer to that all depends on who you ask. You don't have to have one to have a succesful tank, that has been proven by many reefers. But, it has also been proven that a DSB can lower nitrates. So, its really a judgment call on whether your bio load will need it, and if you buy into the logic of it. I personally, like them and use them. The bubbles that perculate up from my SB are proof that it is indeed working. Whatever you decide ....Good Luck!!

[printerdown01]

Sorry Brianc... maybe I wasn't clear in my post (which was certainly my fault). When I said:

I've heard 1-1.5" when using oolitic aragonite

I meant that THIS would work as a DSB, not just as a sand bed. Oolitic not only provides more surface area, but is also more compact due to grain size (much more compact). Which essentially allows anaerobic bacteria to live closer to the surface (since the sand bed is more difficult to penetrate). The larger the grain the more depth will been needed to form a DSB. I think it is a good idea to mix oolitic aragonite with crushed coral: a) it will give you different grain sizes, which a lot of sand bed dwellers prefer and aragonite will play a role in balancing calcium and carbonate levels ("alk" -the indirect measurement of carbonate). If you have way to much calcium in your tank your aragonite will bond the calcium (leaving your aragonite fixed like cement in the bottom of your tank). There is someone on this site that actually had this problem, and some others a RC too... I think it was dave, who told me in a PM that the person had to chisel it out!! The mixture of Oolite and crushed coral will help prevent the massive cement block if you go slightly over -way over and you too will probably need a chisel . I have this stuff and I love it! I have never been so happy, nor excited, with a sand before...

[Brianc_4]

I certainly agree with printerdown about the mixture of oolitic and aragonite, as well as functional its a nice look. But I still question whether or not 1 -1 1/2 inches of substrate can provide a truly anoxic enviornment that causes a DSB to do its work. I understand that oolitic is more compact allowing less flow. But can it really provide an anoxic enviornment with only 25% of the depth of a standard DSB. Also considering the amount of critters crawling and poking through the SB, is there enough room below this activity to produce the layer of low oxygen that is neccessary.Don't get me wrong, I'm not trying to shoot this thought down, I'm just curious and perhaps a little skeptical.

[tinyreef]

i think you'll get greater anoxia in a <2" shallow sandbed than most live rocks in the typical shallow nano settings.

 

the porosity (surface area) of LR is lower than the porosity of sand, even using lava or tufa rocks, so equal volumes the two mediums would not yield equal processing of wastes. a 2" sandbed in a 15g aga is about equal in total volume to a 12" x 8" cylindrical piece of LR (see OxInYourBox's nano :woot: ) but the total volume of the rock cannot always be brought to bear though (i.e. solid center).

 

also the entire sandbed isn't as exposed to a well oxygenated water column as LR. because the sand's surface area is greater, the distance for water to travel is also greater except for truly humongous pieces.

 

critter agitation exists in both mediums. i won't attempt to quantify one over the other but significant water currents are induced by LR inhabitants imo, maybe more so than sand critters (sponges, various worms, nanofauna, and the ubiquitous 'pods').

 

the 4" dimension cannot a ceiling/floor imo without discounting every piece of LR under the 8" cylindrical minimum as well. 4" does work but is it necessary? i don't think it is, just mo tho.

[Brianc_4]

There seems to be a lot of varying opinions on this subject, and I don't mean just on this thread. Other boards, books, magazines, etc. Does anyone know if there has been some hard research done on this? Testing of oxygen levels at different depths with different substrates. Also minimum and maximum oxygen levels required to incur the change from nitrates to nitrogen and oxygen. It just seems that there are a lot of people in this hobby who disagree, but I haven't seen any hard facts to support either train of thought.

[Glenn]

Brianc_4: Try Dr. Shimeck at RC, I think he experiments with DSB's.

[tinyreef]

absolutely no research on my part! i agree with you brian, i'd also like some hardcore evidence to satisfy the 'numbers' guy in me too. when things/techniques work and people say it can't or isn't suppose to, it confuses me ???

 

i'm just a schmoe trying to apply logic to all the constant marketing bs we're all inundated with. new stuff that becomes old and 'accepted' and old stuff that gets re-packaged into new stuff but with a higher price tag.

 

i'm always trying new stuff in the hobby. heck, i still consider my nano to be a continuing experiment from my last nano. and how long have i kept this nano? zero, i'm still trying it. after a couple of years i'll say i'm keeping a nano.

 

it just irks me that certain positions are taken up in the hobby and any deviation from whatever current gospel is slammed. keeping nanos for instance. all you irresponsible people keeping nanos, for shame! "there's absolutely no way you'll be able to maintain the stability in that small of a system!" yeah, right!

[Glenn]

100% correct tinyreef! There is so many aspects to this hobby that it is difficult to say who's methods are correct and who's are irresponsible. I mean look at Dave ESPI and Brandon 429. They are both keeping miniscule reefs that seem to be working. These ecosystem are so diverse and adaptive that the methods of reproduceing them and maintaining them are many. Even though I don't agree with Darwin on the whole evolution thing, I do believe that animals are made to adapt to their enviroment for survival reasons. If they couldn't then we ALL would be extinct right now. It was only a few years ago that VHO was all the rage and people keeping sps swore by them. Now I'm reading articles/threads that say you can't keep them under anything but MH (some say no less than 250w). Go figure? ??? But in the end this is just MO, and is only one of thousands in this controversial hobby.