so has anyone here got an older sandbed (let's say, five years or older) and a huge cyano problem? apparently there's a correlation, and it's that type of thing that i am worried about. also, has anyone here ever seriously disturbed or transfered an older DSB, causing the release of H2S?

I agree Brad, the deciding factor of adding my DSB was the plankton. However, most people with larger particle size and a shallow bed also have plenty of critters, which should equate plenty of plankton.



The fact that you/we add a DSB doesn't mean that detritus isn't there, some of the material is used up and worked through the chain but certain materials do not get used up. They are never eliminated and continue to accumulate and eventually begin to hit toxic levels. It was suggested to me that siphoning detritus is a proactive and preventitive measure.



If you go back to the food and additive studies done a couple of years ago(?) and look at the make up of these items we add regularily to our tanks you have to ask yourself; where do all these compounds and elements go? Certainly some are taken up into the biomass of the creatures we feed but not all of it. Food for thought.

PS: I'm not pretending to know the answer but I was given a few hints, some direct and some not so direct. I'm just one of the sheep trying to figure out which herder knows the most or is closest to right :smile:

(Baaaahhhh humbug.)

One point to consider, or at least my little modicum of knowledge that I want to throw out into this, is that particle size of a sandbed directly correlates to what kinds of infauna it will support over the longer term.

For example, I have a 20g tank with a 4" sandbed in a 10g sump. The particle size is too large for what we would consider a "proper" DSB. In fact, as DSB's go with denitrifying (or whatever the term is), it's useless. The bed is three years old and has yet to develop any anoxic zones. BUT, the reason I don't pull it out, is that it is a perfect breeding ground for larger 'pod type infauna. My 20g is literally white with bugs at night. Of course, of great significance to this that I'm obligated to share (to provide both sides of the story), is that since there are no fish in this tank, there is a limited number of predators for those bugs and that's probably a contributing factor to the overall numbers, but, I'm convinced that the larger particle size is a key factor in this case as well.

The oldest sandbed I ever had was 5 years, but again, it would not be considered a "true DSB" because of the particle size. This was also a plenum'ed tank, and over 5 years I sure saw some pluses and minuses with that type of setup. When I had set up that tank plenums were still "in vogue." Shortly thereafter, they were no longer fashionable and DSB's were all the rage.

Fashions come and fashions go. Some ideas have merit, but rarely do ideas come that are only merits without some kind of pitfall. Sometimes the pitfalls aren't seen until you're well knee-deep in it.

Interesting thoughts though. I guess when I set up my 50000 gallon tank one day, I won't have to spend $200g on the sand after all. Maybe only $10g. That's a releif!!!!!

tony how do you feel about the sand in your bowfront (with the ritteri)?

at this point in time i still think i'll continue with my original plan, 4" DSB.

I guess I'm not hugely worried about it in that tank at this point. I don't forsee that 72g housing the ritteri for a period beyond the next five years anyways, so, .... If I have to replace a DSB every 5 years ... the tank will probably be torn down well before then, or maybe I'll move to a different house by then ... at some point something else is going to dictate that I do something different anyways.

I'm just thinking out loud here ..... One other thing to maybe consider, that I think could be valid, is that sometimes a DSB is good for reasons beyond just the denitrifying. For example, I am planning on redoing my carpet tank, and I plan on putting 4"-5" of sand in there. The choice of this is dictated by that a deep sand bed of fine particle size is the appropriate substrate for a carpet. Whether it denitrifies, or breeds bugs on the side is almost immaterial ... it should be there for the benefit of the animal that is looking for it. Hmmm, again, just thinking out loud here ... It seems to me another example would be this: a bare-bottomed tank would be a terrible home for a jawfish .... although a fine particulate DSB would also be nearly as useless for that fish .... for that fish you'd want a deeeep sandbed but with quite variable sized grains ranging in size up to the "small pebble" size. So again the choice of animal dictates (at least in some cases) the choice of substrate.

I would imagine that anyone attempting to house, say, garden eels, would need like a 12" - 16" sand bed. (Yikes!!!!)

What Delphinus said reminded me of an article I read a year or so ago, basically... a 2mm grain of sand will support different life than a 2.5mm grain, some of the things we are trying to keep like a very very specific size of particle... I wish I could rememer where I read that, Oh hang on.. brain storm...

http://www.animalnetwork.com/fish2/a...wb/default.asp

http://www.reefs.org/library/talklog...ek_090698.html

http://www.animalnetwork.com/fish2/a.../1/default.asp

Couple of links to read and consider.[/url]

Great Discussion everyone. Good point Mitch! Hey Deb I got an extra reactor for sale :razz:

Anyway I agree with Tony's comment's 100%. In the new 230g there will be a DSB as well as my current 90g tank acting as a refugium which has a DSB. I guess I could just have a DSB in the refugium but like Tony said, there are critters that will look for it and it will be there for them and I enjoy the look of sand in a tank..... Chances are that the 230g will be set up for a long time(Yes I plan on never moving now :rolleyes: ). If in 5 years I have to take some sand out an replace it than so be it. 5 years is alot of time to enjoy my tank with a sand and if I have to invest some more money and a day off down the road replacing some of my sand than so be it. Go DSB's Go! :multi:

Good point, Christy!


:razz:

What plankton are you guys referring to that originates from the DSB? Plankton is a general term that refers to tons of little plants and animals that are floating in the water column. :confused:

As far as detritus goes, a properly sized DSB should be able to handle ALL detritus that is produced in the aquarium. Remember, detritus isn't just made up of leftover food and animal solid waste. It is also made up of DOM/DOC and POM floating in the water column. Bacteria will attach to the suspended organics, forming larger particles which then settle to the bottom of the tank. If you have a skimmer operating, it will mechanically remove a portion of the suspended organics, in which case you can "overload" your tank with more than you could with just a DSB. Make sure that you have a properly sized skimmer, though, and that you also have enough water circulation and turnover so that the suspended organics MAKE it to your skimmer.
(sorry if that sounds like a "lesson", I just wanted to make sure that we were all talking about the same thing here... :biggrin: )

As far as toxic chemical buildup goes, i think it's a very real possibility, and that it would be a good precautionary measure to plan on changing the DSB material after a period of time. I have no idea how long though....depends on how much mucking around a person does in the meantime!

Mitch :smile:

Mitch, the plankton referred to is the larvae of the sand bugs. It can account for a large portion of the food available to corals.

Why would it be recommended to change all or part of it out at all, if it could cope all that the tank produces for waste ?.....because it just doesnt.

If the sandbed werent there or just minimal, the skimmer or other filtration would have a chance to take up the extra,and siphoning of detritus could be handled easily if any remained on the bottom.

There is no question, it is a sink.

One should also consider is that the sandbed does contain huge amounts of life...could part of the reason for problems stem from die off of some of this life ?

I sort of look at it like a time bomb sitting under my rock waiting to go off.

The plankton we're referring to when discussing the DSB is the benthic faunas' larvae, sperm and eggs etc. I kind of thought with the area of discussion we were in, it would be obvious. My apologies.

I'm not sure I completely agree with the statement you've made concerning a properly sized DSB. What are you using as an indicator that a DSB can handle "ALL" detritus?

Thanks, guys. :smile: I guess I never really considered that the volume of larvae, eggs, ect from a DSB was that significant.
I don't know how to effectively "size" a DSB, but I do have it in my mind that given a large enough surface area, and the proper depth, of course, that a DSB should be able to handle all naturally occurring detritus material. (which excludes any extra chemicals that would come from our artificial salt, additive over dosing and processed food)
My new set up here has a 180g sump/refugium that has a 4 or 5 inch DSB. I've really noticed a difference with detritus accumulation, or the lack of, compared to the bare tank sump set up I had before. The sandbed in the sump/refugium has NO detritus building up on the pumps, floor ect. I can't help think that if I had a big enough DSB, I could get rid of my skimmer.

Mitch

I'll admit it. I'm a sheep. I first started my tank with a plenum because it sounded good at the time. When I moved up to a larger tank I was told a 4" DSB was the way to go. I guess I just go by the experiences of other people and nobody I talked to at the time had a bare bottomed tank. I kind of like the added glow of the white (well pseudo white in my case) sandbed. I also think it provides a home for a host of critters that wouldn't necessarily be around if I didn't have the sandbed. I also think that the DSB really should be recharged (or at least charged) with new critters (ie. sand exchanges from other tanks) fairly often. I would think that the critters in your tank can't necessarily handle ALL the detritus that the DSB receives.

Does anyone know exactly HOW the DSB becomes a sink for all the heavy metals and such (chemically I mean)?

When you say the DSB becomes exhausted after a few years, what exactly does that mean? What about it becomes exhausted?

Christy :)

Christy, both good questions. How does aragonite become a sink? Are toxins adsorbed?
What is exhausted?? Ca?

Last night I asked a simple question, and Brad gave me a simple answer, which I appreciated. Now when I wanted to give a bit of a rebuttal (not an argument), the thread has really grown. But I still want to make a small point if allowed. The point was that given the small grain size of a typical sandbed, and each grain can be colonised by bacteria. You would need tons, and tons of rock to equal the area for bacteria to colonise. I hope that makes sense, as I am having a problem with the sentence structure. :eek:

In addition some time ago when I hung around Aquaria Central there was a thread about sandbeds where a guy really was upset, and told us the inherent danger of sandbeds crashing, and killing everything. The outcome of that discussion was that there was almost no anecdotal evidence of such a thing happening.

I myself have smaller tanks (the largest being a 50), and consequently I have moved sandbeds a number of times. The only time I noticed some H2S was when I had a six inch sandbed. Since that time I keep sandbeds down to four inches without any problems.

I hope I did not bore you with this. :smilecol:

Sinks? Sources...

The DSB is both a Source and a Sink. These are opposite terms used to denote things that either provide something or take something away. In nature the Mangrove swamps and Seagrass Flats act as a Sink for some of the nutrients produced by the highly productive reef, which is a nutrient Source. A properly set up aragonite DSB is a Source of natural minerals and buffers (Ca, Sr etc.), can be a Source of natural planktonic and larval prey items for filter feeders and corals. If there is a ton of rotting material in your DSB then it is a Source of phosphates and other nutrients that are released by fungi and bacteria. It is a Sink for Nitrate, meaning it absorbs Nitrates. I think a properly set up DSB is better than Live Rock at Denitrifying, but that doesn't mean it has to be in your display, under your lights, accumulating detritus. It can be a separate filtration component altogether, plumbed in line.
As far as DSB's accumulating toxins...Do you mean H2S or Heavy metals?
Aragonite is constantly dissolving so that would release the bonded heavy metals back into the water. H2S is not something I have experience with...It used to be a big concern when LR wasn't being used along with the meiofauna it imports.

Stephen

i get what you're saying bob. the smaller the grain size, the more sand you have in a cubic inch, the more surface area there is, the more critters can live on the sand. the bags of SWC sand jon brought in has some absurd number on it, the exact space available, but it makes sense i guess. the same concept applies to bioballs.

i guess the one thing i can't figure out is, where is the sulphur from the hydrogen sulphide coming from? it's not organic waste, it's not in the water, it's not in the sand... or am i missing something. however it does make sense, that if you're going to have anoxic (is that the word) areas in the sand bed, then there has to be some other gas down there, and H2S makes as much sense as any, i suppose.

Sulpher is an element that is in most organic matter. Food contains sulpher in some form. It's everywhere!!