Are DSB's timebombs?

[biotoxin]

just thought id share an interesting conversation from another forum about dsb's having to be replaced completely due to their nature of absorbing nutrients and gaseous nature. Here's a quote.

DSB's are nothing more than a nutrient sponge in your tank. Period. You can try to explain it away as much as you want, but in the end their sole purpose is to soak up the built up nutrients and junk in your tank. The problem is that we're dealing with a relatively small and finite volume...and it's only a matter of time before it gets full. That's when stuff hits the fan. If you visit various other reef boards, you will see a rather common occurance of those who have had their DSB's up for 4-5 years...and their tanks have gone straight to hell. Even the LR becomes oversaturated with nutrients, leading to uncrontrolled nuisance algae, coral bleaching, etc. in tanks that were otherwise thriving and healthy. Once the DSB is saturated, the only option is to COMPLETELY REPLACE IT. You can spend money every year introduce new fauna packages from various vendors and recharging it with biodiversity on an extremely regular basis...but at some point its going to reach maximum overload. All this to avoid siphoning out some crap every once in a while.

It was my understanding that in a reef tank we are simulating the effects of a natural ocean but as our sandbeds remain static and not moved around by tides it would seem to me that this quote is true and that indeed the buildup of waste in a dsb is an inevitable fact.

The problem is that the conditions of a typical DSB is the complete OPPOSITE of conditions on the natural reef. In nature, much of teh sandbed is actually aerobic, with smaller portions being anaerobic or anoxic. In our systems, it's the anoxic areas that comprise most of the DSB because that's the part that takes care of denitrification and that's the process we want to occur. Not so on the reef. The DSB is NOT creating natural conditions in your tank...don't be fooled by that statement.

 

[snapcrackler]

Perhaps those that do not have proper sand stirrers (assarius, cerith, bristeworms, stars, gobys) in their tanks are the ones that run into that problem. If you have a dsb full of beneficial detrivores and sand stirrers then it would seem you could run indefinitely without problems.

But if you have a DSB without those organisms it just becomes a yuck trap.

Just my 2cents.

 

[wseaton]

If you don't have such a deep sand bed (around 3-4") you won't have to worry about the anoxic zone being such a threat.

 

[biotoxin]

after a while tho it would seem that even those clean up crews cant get all the detritus and the sand gets "used up" and less soluable. My question is whats the alternative? Plenums? CC? Barebottoms?

 

[snapcrackler]

I don't think it is the literal soluability of the sand that does anything since sand is actually silica which is pretty nonporous, but the sand just creates an area for the beneficial bacteria and detrivores. Therefore it would never get used up in that sense. The beneficial bacterial and detrivore cycle would just keep going.

BTW I am just purely speculating from what I understand, I have never had a DSB, I run crushed coral at 2-3".

8)

 

[biotoxin]

well heres the link if anyone wants to get the full story.

http://www.nano-reef.com/forums/showthread.php?s=&threadid=19019

 

[snapcrackler]

Thank you for the link, I have a lot to learn about DSBs myself, I'm just speculating and therefore trying to understand it better myself.

 

[silverain420]

So does anyone have any suggestions for caring for jawfish? They of course need a DSB. Do they stir the sand up enough that I would not need to worry about it, or do I need to replace the sand in a couple of years? My DSB is about 6 inches, 4 being live sand, and the remaining 2 or so is CC. I also have a purple firefish that has made a burrow in the sand as well? Will this be enough to not have this problem further down the road?

Jen

 

[loganj]

This has been an ongoing debate with folks lining up on both sides. OTS (old tank syndrome), to my knowledge, has not actually been documented anywhere and is still pretty much a theory. It would be an expensive and lengthy experiment to test it. Most of the sand we use in SW tanks is aragonite and will dissolve over time...silica sand can be used but is not recommended for best results. It would be interesting to have some sand from an old tank tested to see exactly what is in it. To really prove it though, you'd have to set up several tanks, run them exactly the same, and take regular samples of the sand for testing over a period of 4-5 years. How one would go about doing that without disturbing the anoxic areas in the sandbed is beyond me though. Personally, every tank I have uses a DSB. JMHO.

 

[MACATUA]

It kinda comes down to personal preference, eh? Like they say, there si more that one way to skin a chicken.

 

[RogerMcAllen]

I am no SW expert, but couldn't you just swap out a few cups of sand every once and a while? Just goto the regional forums and donate a few cups of your sand to a newbie. This will help seed them and allow you to replace your old "used sand".

 

[biotoxin]

Sounds like a good idea, id just worry about trapped gasses in the sandbed. On my next tank im going to use a plenum and a medium sandbed around 3" with the deeper sandbed in a refugium.

 

[loganj]

Biotoxin, if you'll do some more looking, you'll find plenty of folks who'll tell you that a plenum is a nutrient sink and will eventually destroy your tank. Yet many aquarists use plenums and have for years without a problem...same thing with DSB's. There isn't really any "correct" way to set up a SW tank...there are several ways that will work with each having it's pros and cons. As I said before, I'd love to see some conclusive data regarding both plenums and DSB's...someone else will have to do it though...I can't afford to .

 

[biotoxin]

ya i agree there are many ways to do a tank and many success stories with and without DSB's/Plenums etc. When it comes to duplicating nature i think we really do what we think is right instead of things just doing what they do naturally through evolution. I think we're still just learning about reef systems and maybe in 10 years there will be at least some conclusion on the degredation of a sand bed. Who knows, maybe it gets better over time.

 

[reefrunner69]

There is a rather lengthy thread here at AA.com that discusses the problems or not, that DSB's have.

http://www.aquariumadvice.com/viewtopic.php?t=1494

This can become a rather hotly debated topic, so let's keep in mind, everyone's opinion is just that, an opinion and all are valid

 

[sumphead]

I was always under the impression that aragonite DSBs deteriorate at approx the rate of 1/4" to 1/2" anually. If this sand is replaced anually refreshing the DSB, there seems to me, no problem at all. A deeper DSB in a fuge sounds very logical as well. As for silica sand, I shrug. However the occasional sand swap without going to deep under the surface as Mr. McAllen has pointed out sounds logical as well. In my very limited research and knowledge I will make a prediction just as "those other guys" have. (I am very loyal to my friends here at AA!):

-The plenium will retire to the clearance rack just as the UGF and the tapered leg levis.

LONG LIVE THE DSB!!!

-thanks for allowing me to throw my opinions and theories out.
R-

 

[biotoxin]

I can see the theories and scientific information behind dsb's and they do have a proven reputation. I think the main argument is from those that have dsb's and dont take care of them properly. After all, it only takes a few people with dsb's that fail to spread misinformation.

 

[wseaton]

Anybody ever here ever of this new invention called a 'gravel vac' and siphon tube?

:- )

The greater problem with a DSB is that metals and otherwise inert materials slowly build up and creates this toxic/anoxic layer that eventually collides with the aerobic layer, and then 'boom'. The actual deterioritation of the substrate material itself, usually arogonite or CC, isn't a problem.

Another thing I do with my tanks is keep a shallow layer of sand in certain parts of the tank so my tank bottom isn't uniform. This would seem to keep the dreaded anoxic layer at bay because it's not static.

I wish I could discount DSB's for certain, but considering I tend to over-feed and over-stock *and* my nitrate levels are near zero, I just can't discount them.

 

[fishfreek]

Anybody ever here ever of this new invention called a 'gravel vac' and siphon tube?

What about it? Are you suggesting we remove our sand beds vis a syphon and replace them on a regular schedule?

If something was to develop a toxic layer of gas it would be the plenum since the entire concept of one is to intentionally create a space that is nearly void of water flow.

I have and will continue to use DSB's until I suffer a great crash of my ecosystem. There are just way to many factors in peoples tanks to try to formulate what caused what. It could be so many combonation of things that could lead to an issue where as two people with the exact same setup might not experence the exact same problem because maybe 1 perosn feeds less or feeds more or has less fish or more fish or has 1 less sand sifter, etc.

 

[biotoxin]

thanks for the feedback guys. I dont see a plenum on the ocean or a clear glass bottom when i go to the beach so ill stick with dsb's for now