Sand bed thoughts

[EmilyB]

Some discussion on this during the Victoria tank tour....just thought I might start a thread here for some of the people who've kept a sandbed for a longer period.

I'm removing the bed from the 120g, but I have been wondering about the whole thing since I switched from a shallow cc bed a few years ago.
I had a LOT more life, but I did have probably 2lbs live rock per gallon.

Originally, I was going to replenish some sand in the 155g (four year old sand bed)...now I don't think so.

Thoughts?

[SuperFudge]

Hi Deb,

I do love the look of the DSB,but i have really come to think the benifits may not outweigh the potential long term problems. (more so in the main display)
This last sand bed i have had has followed me through several tanks and some of it is over 5 yrs old.
I have always thought i had a healthy sandbed,but lately i have fought with redish cyano trying to cover the substrate,and even with the addition of goodies from a rock curing vat it still had slowly gone down hill.
I did add new sand aswell, but i couldnt place the blame soully on that reason either.
I also am sure the critter population for the sandbed turnover was excellent,i had a tigertail cuke,conch,about a million stomatella and other sand dwelling snails.
Yet when i just tore the sandbed down,it seemed just like a a big cesspit of sulphide and detritus.
I understand these anoxic portions are supposed to be there,but it hardly seems a benifit to the system water quality.

I have no doubt that a sand bed adds a whole range of benificial life to the system, but after removing atleast 200lbs (ya,i was panicking) from there the corals or fish look nor act any different than before....even after a transfer into a large tub.

I guess it will have to be a little more long term before i could say that there was a significant benifit in removing it, and im yet unsure if nitrates wont rise like crazy..but i would guess that a small,managable and semi-routinley siphoned sandbed in your refugium would be just as benificial, Live rock accomplishing the rest.
( I cringe at the thought of all the guys right now that would like to jump on me for saying so :eek: )

In the future i will be setting up another reef,and i know I wont have a sandbed any deeper than enouph to cover the bottom glass, even if in the end it is only for peace of mind.

I really believe it would be ,overall just as sucssesful a system or even moreso than a tank with a DSB.

Alright.....Let me have it. :eek:

[Jack]

When I took down my 110 gallon reef w/5-6 inch DSB the sulphide smell and dirty grey water that was left behind was a cause for question with me. On my new 120 gal I didn't want that in there, plus it took up valuble hight in the tank so I went with a small sandbed (1/2 to 3/4 inch medium grade aragonite bed) but it just didn't look as awesome as a fine grained DSB. I also was wondering If I was loosing benifitial aspects of the DSB so I came to a comprimise and I added a bit more than 2 inches of sugar sand. It looks good and I hope I get a lot of sand bed life. For "nitrate reducing" I went with a 4-5 inch DSB in a 20 gallon refugium and hooked up to my sytem.

Now am I getting the same filtration that my 110 gal had? I think so. The way I look at it, at least this sandbed in the rubbermaid refugium can be replaced in a few years, if it is proved that they need replacing or refreshing.

I'm interested to hear what people think about this aswell, so post!

[christyf5]

I am a sandbed.
I have worms crawling in me.
Eeww gross!
Get me outta here!

- Sandbed Thoughts

[SuperFudge]

http://smilies.networkessence.net/s/contrib/edoom/iamwithstupid.gif

[AJ_77]

I am a sandbed.
I have worms crawling in me.
Eeww gross!
Get me outta here!

- Sandbed Thoughts
Now THAT's funny!

[smokinreefer]

the one thing i like about a thin sand bed, is the notion that if it looks dirty, you can siphon it out, clean it and put it back, or just replace the thin covering, and then the tank would look all purdy again! ofcourse providing the tank has sufficient biological filtration to sustain the tank, without causing any spikes when the sanded is removed.
just a thought.

[ron101]

Sounds like 'old tank syndrome'. I remember reading a few posts over in Shimek's forum on RC about old sandbeds. I believe he was saying that after several years accumulated detritus and bound-up nutrients can start to cause problems. He doesnt recommend re-using old sand.

I guess according to his info, one should tear down the tank once every several years and clean or replace a portion of the DSB. I can't wait...

[SuperFudge]

Sounds like 'old tank syndrome'. I remember reading a few posts over in Shimek's forum on RC about old sandbeds. I believe he was saying that after several years accumulated detritus and bound-up nutrients can start to cause problems. He doesnt recommend re-using old sand.

I guess according to his info, one should tear down the tank once every several years and clean or replace a portion of the DSB. I can't wait...

Thats what i had done...it did not work in the slightest.
I am not a scientist, but i really think most of that is bogus.

What then about the rock ? It would have the same problems aswell,yet noone tears that out and replaces it.

So If there is nutrient/detritus build up to toxic levels within the sand bed, then its really defeating its original purpose.....the whole idea of the DSB was to support the planktonic life to process these organics.
And it clearly doesnt.

If there were no sand bed at all, the end result is the same....you still end up having manually remove the stuff anyways.

[Aquattro]

What then about the rock ? It would have the same problems aswell,yet noone tears that out and replaces it.

.

Marc, I recall reading that Dr. Ron recomended replacing rock every 5 or 6 years or something like that.

[SuperFudge]

Brad,
For Some odd reason, that doesnt surprise me. :wink:


Heh,

I find it kinda funny, Old tank syndrome.....I think its a theory to cover up other theories that clearly didnt work.

[Quinn]

i have nine bags of SWC aragonite sitting downstairs. on saturday i was planning to put it in the tank. do i do it or do i not? what other ways are there to reduce nitrates other than a huge amount of live rock or some antiquated filter system? i thought DSB's were the latest and greatest...

[Troy F]

If it's any concellation TeeVee, I had the same concerns with my tank about a year ago. I decided to go ahead with the sand but in all honesty, I regret it. If I were to do it again I'd have not done it. You'll have to make up your own mind based on the hours of reading that are available on the various boards. Keep in mind that much of the information available is heavily biased towards adding DSBs because...well, most of us are sheep. For arguments against, look for Richard Harker comments as well as Bomber/Spanky/Landescaper to name a couple.

[Quinn]

ok well looks like back to the old drawing board. perhaps i'll do a very thin layer in my display, so it doesn't look weird, and a very deep one in my sump (9" or something?). what do you guys figure? sump is approx. 17 gallons, main tank is 150 gallons.

[Diomedes]

I don't use DSB's any more. Right now my tank is bare bottom, but I am going to use a combination of Thorite cement and live rock fragments to produce a molded rock bottom for my 75, and for the 300 gal tank I am ordering in a few months. I can keep the current as vicious as I want hehehe since the corals I will have in there appreciate that sort of environ. No need to state my reasons...Troy just hinted at some research the interested party could do...Anthony Calfo's book details some good plans for denitrification that negate the need for a DSB, and you still get all the benefits. But aside from that I am tired of the look. How frequently on the reefs do you find little patches of sand with a couple of large rocks with corals sprinkled all over them like fruit salad? Not too often. Large corals, small fish. Expanses of sand, large rock and cliff formations.

Stephen

[SuperFudge]

Keep in mind that much of the information available is heavily biased towards adding DSBs because...well, most of us are sheep.

AMEN !

[Quinn]

you know this is the beauty of science - some scientist comes up with some theory, does a few basic experiements to prove it, does a fairly good job, and everyone jumps on board. and when the whole world is heading full tilt in that direction, anomalies start popping up and all of a sudden it's time to reevaluate and change everything yet again. in high school physics it wasn't such a big deal... now that i'm spending money on it... A$&%&$@#!!!!

i will continue to read up on this as i get closer to "the day". i like the look of some sand, but one inch is as good as four to me as far as visual appeal goes. i am going to research some other methods of N-removal. i think running a very shallow sand bed in the display tank and a deep one in the sump would be a good idea, as the sump is far easier to get into, move around, and, if the time ever came, empty and clean.

[Aquattro]

Until recently (when I added more sand 'cause Ron told me to) I ran about 2 inches of sand in most of my tank. I had no nitrates and lots of sand fauna. Sand looks good, and that is the extent of my opinion.

[Quinn]

whether they're sheep or not, it looks like everyone does DSB's. the alternatives are either huge water changes, a heck of a lot more skimming, or a wet/dry. it seems like a lot of people agree DSB's need to be changed every few years. i think i'll continue with my current plans, 4" in the main tank and 5" in the sump.

[Aquattro]

Quinn, you can keep a tank nitrate free without any sandbed. That's what the rock is for. I keep a sand bed for plankton production, not NO3 removal.
The 1.5 pounds per gallon "rule" came from needing that much rock to perform nitrate removal. If you have a lot less rock, or extra heavy bioload, then sand certainly can help.

[Quinn]

i plan to have a lot of rock. i wonder if it would be intelligent to do one or two inches of sand, for the looks? i don't want a bare-bottomed tank.

[AJ_77]

My first sandbed, 4" - not so good as far as practicality and esthetics. But, it was disturbed and moved, and was the finest grain.

Second sandbed, second tank, 3" - worked well, looked good. Larger grain size mix, different colours too. Lots of life.

Third sandbed now, ~3" with a skiff of gravel on top. So far so good. A little ugly, but seems to be harbouring the necessary life. Crabs are constantly going over it as well, and it is quite clean, has the requisite layers visible from the front, colours, bubbles, etc.

Some of the nicest tanks I've seen in pictures though, had the thin mixed substrate, almost a "grunge" look. Could we be converting to Garf methods??

:eek:

[Bob I]

Quinn, you can keep a tank nitrate free without any sandbed. That's what the rock is for.

Okay, I have missed something. Could you point me toward some reading material which states LR removes Nitrates?

Thanks. :confused:

[Aquattro]

Bob, I'll try to find some material, but before the sandbed craze, that's all that was used. The anaerobic areas in the rock house the bacteria required for denitrification. My first reef tank (bare bottom) had no nitrates.
A sand bed may/will allow greater stocking capacity, but the rock will remove nitrates. This was the technology in the mid 90's.
Most reading material I have is printed, ie, older FAMA mags. I'll see what I can dig up electronically.

[Aquattro]

Some stuff here.

http://saltaquarium.about.com/library/weekly/aa111901a.htm

particularly the quote from Deelbeck near the bottom. Very brief, but gives you an idea of what the rock was originally intended for.

[BCOrchidGuy]

Supposedly, LR that is porous will have anoxic regions in it... Thus we should get nitrate removal.

For what it is worth I don't think a 9 inch sand bed will do any good. Stick with 4 inch, it has been proven to be the best depth for a De Nitrifying sand bed. I keep about an inch to an inch and a half in my 90 and 4 inches in my 40 gallon refugium. I have about 60 Lbs of LR in my tank and about 20 Lbs in my refugium. I do 10 gallon/week water changes and I have no nitrates.... is it the DSB or the water changes??? I don't really care, I'm just happy that I don't have problem algae, and I do have healthy corals and inverts.. (or so they appear healthy).

[StirCrazy]

there have been studies that have showen that a proper DSP is more efficient in removing nitrate than LR. so does this mean we don;t need LR.. nope not in my views, what it does mean is that if the design you like calls for less than 1.5lbs/gal you can do it. I started that way but something happened and I ended up with about 2 or 3 lbs/gal :rolleyes:

Steve

[Aquattro]

Steve, we're suggesting you don't need sand, not rock.

[StirCrazy]

Steve, we're suggesting you don't need sand, not rock.

ok well to be different let me sugest you don't need rock but you do need sand :silly:

seriously the trend which is cool seams to be a nice sand bed and small piles of rock.. this way you can actuly let the corals build the reef.

Steve

[Troy F]

I still think you're missing the point of the discussion. We're discussing whether or not a deep sand bed is worth the trouble. There's no doubt the sand acts in reducing nitrate, what is being questioned is the long term safety of one.

[Aquattro]

Troy, the problem is there isn't a lot of long term DSBs to evaluate. So far it's a good thing, with only suspicions of bad things

[SuperFudge]

Troy, the problem is there isn't a lot of long term DSBs to evaluate. So far it's a good thing, with only suspicions of bad things

Heh, this is exactly why it should make people wonder whats so good about a DSB and the recommendation for one by our peers in using one for the long term.

Its a good thing compared to what though ?

If vs a shallow sand bed, i would think the question vica-versa.....overall, a reward of a just as healthy system with no sandbed, and suspicions of bad things to happen with a continuously degrading DSB...

Some good thoughts here.

[Troy F]

Troy, the problem is there isn't a lot of long term DSBs to evaluate. So far it's a good thing, with only suspicions of bad things

Good point Brad. The reason I hesitated on setting up my DSB was just common sense; eventually a critical mass has to be reached doesn't it? I never doubted the denitrifying effect, I just worried about the long term success. I'm told that there will be information released in the near future that will be very informative and when you see the theory behind it you'll laugh at the simplicity.

Dr. Shimek himself has stated that the best place for one is apart from the main display and also, he recommends recharging your sandbed with detrivore kits yearly. These are two things few of us have the space or capital for.

[Aquattro]

I still think the contribution of a sand bed, as far as plankton goes, is a good thing. I'm not sure how to replace that without a remote DSB. I also don't know that a DSB acts as a sink.....does it? Got proof? Does it reach critical mass? These questions are way over my head, so acting as a sheep is the safest way to go. Certainly, given the time, money and space, it would be great to experiment. But since I have 1 tank that must work, I must follow what works for others. Of course, when all others fail, I fail too, but pioneering isn't my thing.
So, is a DSB bad, good, or indifferent? Really, we don't know.

[stephane]

I have convert my self to DSB last years after many years of keeping my tank bare bottom and I haven't found any real positive effect of it till then
but some negative one so my next reef will be bare botom

[Aquattro]

Stephane, what type of negative effects?

[stephane]

-It take a lot of space in the tank
-look dirty on the glass with all sort of color from green black brown.......
-I realy can't have the flow I want or it made sandstorm and dig hole everywere
-My 10 years old blue damesel play all daylong diging in the sand and splach it everywere on coral (I can't get rid of him he is the first fish I cycle the tank 10 years ago and It'a love story between him and me :mrgreen: )
-I have to be realy more carefull when I clean the glass to not scrach it in the bottom
those are the main one It's not big drawback but enought to ask my self why in the world I have put money,and time in this. At least it give me experience :mrgreen:

[Michael]

Well...this is one discussion I can't stay away from.
For those people planning to have just a thin layer of sand rather than a thick sand bed...you will get the same problem. Meaning that the ugly red coloring on the sand, and it looking ugly will still happen.
Currently my sandbed is thin, only a half inch, and I still have had the problems mentioned here. I was about to go to a thick sandbed...but now an re-thinking the idea.

-I guess without a sandbed there are certain animals you can't keep...ie cucumbers, brittle stars (although mine stays on the LR, so maybe you coud keep one). For the people having a clear glass bottom, are there any animals you haven't been able to keep (that you wanted to keep) :question:

-If a livesand bed was crawling with animal life, then wouldn't it accomplish its goal of converting harmful substance to less harmful? But I guess it would be like using a canister filter...the less harmful substance would still be in the water, not removed.

-Well, that's all my thought/questions for now. I guess I'll be like a lot of us now and re-thinking the usefulness of sandbeds :eek:

Michael

[MitchM]

(I can't get rid of him he is the first fish I cycle the tank 10 years ago and It'a love story between him and me :mrgreen: )


:lol: I know what you mean! :lol:

I prefer having a DSB because it more closely replicates the natural reef.
The problems and issues that come along with it teach me more about the limitations of our little glass boxes.

But pratically speaking, I think that a DSB reduces regular maintenance in a reef tank. I too had a Berlin style bare bottom for a few years, and my observation was that the bottom of the tank accumulated detritus and chewed up LR that needed to be vacuumed out. Vacuuming a reef tank isn't what happens in nature. The buildup beneath the rocks was out of proportion, too - WAY more detritus than chewed up rock.

If a DSB is still having detritus build-up, then perhaps the bioload in the tank is too much for the DSB to handle. Deeper isn't the solution. More surface area is. All those DSB critters have to come up for "air" sometime. Get a separate sump/refugium going with nothing but a DSB in it.

Mitch :mrgreen:

[MitchM]

Oh yeah....and without DSB's, Em would have to go out and buy a CA reactor!

Mitch :mrgreen:

[Quinn]

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?

[Troy F]

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:

[Delphinus]

(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!!!!!

[Quinn]

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.

[christyf5]

http://www.smilies-world.de/Smilies/Smilies_Animals_1/sheep.gif

[Delphinus]

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!!!!)

[BCOrchidGuy]

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/aqfm/1997/oct/wb/default.asp

http://www.reefs.org/library/talklog/r_shimek_090698.html

http://www.animalnetwork.com/fish2/aqfm/1999/june/features/1/default.asp

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

[Canadian Man]

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:

[MitchM]

http://www.smilies-world.de/Smilies/Smilies_Animals_1/sheep.gif

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:

[Aquattro]

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.

[SuperFudge]

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.

[Troy F]

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?

[MitchM]

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

[christyf5]

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 :)

[Aquattro]

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

[Bob I]

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:

[Diomedes]

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

[Quinn]

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.

[Aquattro]

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