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Sand Bed Depth?


sweevo

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Just wondered how deep a sand bed you can realisitically have in a tank before you run the risk of encountering DSB issues? I've looked into DSB's a lot these last few days and have decided to abandon my plas for one and just have a few inches of Arag Alive in the bottom of my tank.

 

Is it a simple case of the deeper the bed the more the risks?

 

Could a 2"-3" Arag Alive sandbed give me problems a year or two down the line? Should I just stick to around 1.5" or less to be safe or am I being over cautious?

 

The tank in question will be a 29G with a surface area 30" x 12" and will eventually stock a pair of clowns, various soft corals, snails and red legged hermits.

 

All opinions gratefully recieved. :)

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My major issue with sandbeds is that detritus can and always will collect on them...its just that simple, no matter the depth. If you don't have enough in-fauna to deal with that detritus (which is very hard to have in a nano), its going to accumulate and "bite you in the ass" so to speak, in the future. For this reason, I like to run my tanks bare-bottom or with a very light layer of crushed coral (old Berlin method style). That way you can: 1) point flow directly at the bottom of the tank and hopefully keep detitus suspended in the water column where it can be skimmed or eaten by corals, 2) vacuum the bare-bottom/CC if too much detritus is accumulating there.

 

Of course, running a tank like this also has its own detriments...the most obvious being that you can't really keep any sand-dwelling or sifting organisms..lol. But we all make trade-offs.

 

The substrate debate is one that could go on forever, I guess all it comes down to is gathering opinions and figuring out which one you'd like to attempt...knowing the benefits and the detriments to each method. This is what it sounds like you're doing here in this thread, so kudos to you..and I hope that others post different and/or conflicting viewpoints, this may end up being one of those threads that others look to when they want to find out about substate.

 

Cheers,

Fred

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EtOH_is_good

my tank is barebottom right now because im planning to still drill my tank. since i've set up the tank (>2 months), more than enough detris has collected on my tank bottom to provide nutrients for limited growth of whatever would dwell in a dsb. so fac wny, is right that whatever your depth there is a possibility of a problem. i thing i read it in calfo's coral propagation book that dsb don't really create problems in the first few years. in previous threads i've suggested shallow substrate levels less than 2", but still other nanoreefers say that is deep enough to create a dsb. i still don't think that is deep enough to have anerobic conditions esp if you have a diverse population of microfauna. so i guess, you'll get all kinds of info but most of it's still debateable. it all really doesn't matter because more than likely you'll want a bigger tank in your near future.

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I had a 1.5" sandbed and I still got anaerobic pockets (the black areas) in my sand. Nothing bad ever happened....except I did see alot of no2 bubbles rising out of the sand after the cycle.

 

Mike

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Anaerobic zones in a 1.5" sandbed....I doubt it..check out this http://www.reefkeeping.com/issues/2004-07/.../nftt/index.htm , the sandbed in question there was over 4" deep and there were NO anaerobic zones. The black areas in your sand bed were more than likely detritus pockets taken over by cyanobacteria for processing. And are you sure they were N2 bubbles and not H2SO4 (I believe thats the right formula for hydrogen sulfide) gas?

 

Just very very very suspicious of anything resembling a sandbed nowadays...lol.

 

Cheers,

Fred

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H2SO4 is sulfuric acid..

 

I like 3+" beds in my tanks.. But my interests lie not just in keeping coral, but actually studying the entire eco system as it occurs naturally. (Or at least to the best of my ability)

 

Either way, there will be challenges..

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I'm relatively sure these were anerobic pockets...The sand was very fine and I never distubed it. I never had a cyano probs. either. I assumed the bubbles were NO2 because I only saw them after the cycle and my nitrate kept going down w/out water changes.

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holyherbiness

I run a sandbed on my aquarium, just because I like the look of it more.

Like FAC said, problems regarding sand beds will occur at any depth.

 

 

Hydrogen sulfide is H2S

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isn't the whole point of a dsb to do exactly what sobe was saying happened in his tank: NO3 gets converted into N2 and bubbles out of the dsb, thus lowering nitrates and exporting nitrogen from the system. isn't this a good thing?

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The only way I can see you having a problem in your DSB is if you dont have anything sifting it OR the fine silty layer on top is too thick..

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The "problem" with DSB's is that they have a shelf-life, so to speak. We can't (and don't) maintain a high enough level of biodiversity in the bed to process all the nutients that we "expect" it to process. Therefore, detritus and phosphate accumulates in the DSB slowly (we do maintain enough diversity to process a large portion of the nutrients), over a period of years, and eventually it "fills up". When a DSB "fills up" it starts "pushing" all of the crap that we don't want in our water comumns back into the water column, effectively overloading the current bio-filter in the tank. Therefore, while a DSB is a great medium-term solution for the removal of nutrients, a better long-term solution is to either run bare-bottom (the ability to remove detritus visually as it accumulates AND to better keep it in suspension via increased flow so that it can be taken up by corals/other organisms and a protein skimmer) or to have a REMOTE DSB, in another tank, which you can shut off from the system when it needs to be changed. Its all about nutrient export in reefing..just as on a natural reef. (On the natural reef the nutrients are exported via the tides, pushing nutrients into coastal mangroves and seagrass beds, and pulling them back out to sea) Everyone needs a method of nutrient export in their tanks..preferably several. For instance..my systems all use waterchanges (probably the most common and least effective form of export) and heavy protein skimming to remove excess nutrients. Other systems used Algal Turf Scrubbers that remove nutrients by the culling of algae from the scrubber and the ability of the algae itself to process high levels of nutrients in a true ATS system. Refugia can be used to remove nutrients as well, provided you're culling macroalgae from the system at a regular rate. DSB's can also work well for nutrient export, provided you realize that you WILL have to change them every few years. (Thereby "exporting" all the trapped nutrients) Sometimes we don't realize we have to take out what we put in, over the long term.

 

Cheers,

Fred

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Hey, I have always used a couple nassarius snails to combat the problem of detritus, etc. in my sand bed. The dudes move very fast and seem to get the job done. I know they airate the sand since they are constantly on the move. On www.liveaquaria.com they have 2 types if you're willing to try that solution. One is a smaller version and the other is what I kept in my 29g. Wouldn't they help a lot w/ the problem?

 

Connor

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"opposed to the small ones?"

 

wouldnt nutrients build up in a shallow sand bed as well? and are there other ways for nutrients to build up in a sandbed besides detritus, if not then how would these buildups get deep in the sand and why would it make a difference whether you have a deep sand bed or a shallow one

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EtOH_is_good

both types shallow and deep will collect nutrients because of the lack of diversity to neutralize them. advocates for dsb would argue that a dsb can neutralize the nutrients. as fac says, the shelf life will eventually end and the dsb cannot keep up with the nutrients. supposedly, the nutrients will then be leached back into the water without being processed and thus causing problems. with a shallow bed, hopefully stuff won't get trapped long enough to cause problems. there's a higher chance that the nutrients will get into the water and be exported with a water change. in another thread, xx pokes fun at me because it seems that im an advocate for bare bottom tanks because there's really not good solution. my counter arguement is that more than likely an upgrade is in the future, so a shallow substrate layer is visually appealing and not going to cause short term problems.

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If you're just going for the aesthetic appeal of having sand in the bottom of the tank, why not just vaccuum it regulary to remove the detrious build-up? You'll be removing the advantegous of a DSB, but you'll avoid future problems.

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Thanks for all the input guys. I decided last week to do what bill_m3 has just suggested, ie vaccuum the sand bed, like I did with my old 7G Nano.

 

I'm probably going to opt for a 2mm+ aragonite substrate (approx 2-3" deep) and just vac different sections of it each week or so to help keep things in check. It would've been nice to have a fine sand bed and be able to leave it to it's own devices but it just sounds to me like it's just not worth the risk.

 

Thanks again. :)

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what do you guys think of what bill said? i'm curious because there is a possibility that i could go dsb and get a pair of yasha gobies and pistol shrimp (the deep sand bed would be so they could burrow more like they do in the wild). the sandbed would also be mixed with crushed coral or larger rubble for structure-would this make a difference as well?

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