lduncan Posted February 21, 2006 Report Share Posted February 21, 2006 Sure, but that doesn't change what sand beds do, and how they work. Layton Quote Link to comment Share on other sites More sharing options...
lduncan Posted February 22, 2006 Report Share Posted February 22, 2006 science and reality almost never go together That's not true at all. People say this all the time (usually when they have an incomplete understanding of what's happening), and it's nothing but rubbish. Science is all about finding the truth. Layton Quote Link to comment Share on other sites More sharing options...
wasp Posted February 22, 2006 Report Share Posted February 22, 2006 Truth is there's some great tanks with sand. Quote Link to comment Share on other sites More sharing options...
lduncan Posted February 22, 2006 Report Share Posted February 22, 2006 ... and the truth is also that those same tanks have sand which cycle phosphate. Quote Link to comment Share on other sites More sharing options...
Pies Posted February 22, 2006 Report Share Posted February 22, 2006 The back pedaling begins... Pie Quote Link to comment Share on other sites More sharing options...
suphew Posted February 22, 2006 Report Share Posted February 22, 2006 I'm hoping you can explain how the 'cycle' side of this works? I can understand in the sea where storms etc happen and all the PO4 etc in the sand bed gets disturbed, ends up in the water then works it way back into the sand bed, but this doesn't happen in a tank. I can only think of it like a glass of water where the glass is the DSB and the water PO4, water goes in, then the glass gets full and the water over flows, but the water in the glass says there it just wont take any more, the water doesn't suddenly leap out of the glass so it can stop over flowing and start filling again?? Is a DSB the same, does it fill up over time, then once full just stops absorbing more, why would the absorbtion reverse and start flowing back out of the DSB? Why would the PO4 start getting higher than the extra that is being added to the tank via feeding etc? Surly if it is the case that it just fills up and is therefore just full, why is this such a "time bomb", why can't the sand just be removed and replaced, or vacuumed, start using PO4 resun, etc? Quote Link to comment Share on other sites More sharing options...
lduncan Posted February 22, 2006 Report Share Posted February 22, 2006 Ok, here goes: While stirring an established sandbed is one way to initiate the release cycle, it is only one of many. Temperature and pH are other ways. All that needs to happen is a decrease in oxygen levels near the water sediment interface. The process is driven by bacteria. The same bacteria which are responsible for the reduction of nitrate: From http://www.ozestuaries.org/indicators/w ... rients.jsp Water column phosphorus concentrations have also been shown to increase under anoxic conditions [17]. This is because some of the iron oxyhydroxides that bind phosphate are converted to iron sulfides during sulfate reduction (an anaerobic process) and the iron sulfides cannot bind phosphorus [4]. The extent of phosphorus release from sediment is also affected by pH. Low rates of phosphorus release from sediment occur in the pH range from 5-7 [18]. From http://aem.asm.org/cgi/content/full/66/12/5236 Microorganisms involved in this process are capable of phosphate uptake in excess of their metabolic requirements and store phosphate internally as polyphosphate (polyP) polymers." "they require alternating aerobic and anaerobic (or anoxic) conditions. Under such conditions phosphate is released in the anaerobic zone and stored as polyP in the aerobic or anoxic zone." "It was found that phosphate was removed from the medium in the presence of oxygen" "Phosphate uptake with oxygen and nitrate took place in excess of the metabolic requirements of the cells since phosphate was released into the medium when the oxygen supply was stopped or when all nitrate was depleted" Quote Link to comment Share on other sites More sharing options...
wasp Posted February 22, 2006 Report Share Posted February 22, 2006 I'd be interested to see any of that quantified. As presented, it is too vague to have any useful relevence to an aquarium. Quote Link to comment Share on other sites More sharing options...
lduncan Posted February 22, 2006 Report Share Posted February 22, 2006 It's a broad ranging process. It's involved in the eutrophication process, and is well quantified. It happens in the ocean, it happens in estuary environments, it even happen in freshwater lakes. Any reasons you can think of why it wouldn't work in an aquarium? You haven't met some of the "scientists" around here either. If you think for one minute you can get those lard butts out of their AC's and out in this heat to look at some mud, ....... These studies are generally (not always) done both in the field, as well as in the lab, using controlled aquariums. The controlled aquariums allow them to verify their findings in the field. Surly if a DSB is a natural form of filtration, it works just like in nature? Or is it better than nature? Layton Quote Link to comment Share on other sites More sharing options...
Pies Posted February 22, 2006 Report Share Posted February 22, 2006 Vague is right. Maybee if you argue it long enough it will become true... Quote Link to comment Share on other sites More sharing options...
0pius Posted February 22, 2006 Report Share Posted February 22, 2006 Not to throw fuel on the fire but don't forget science isn't always right. Things get disproved later down the track all the time. Quote Link to comment Share on other sites More sharing options...
wasp Posted February 22, 2006 Report Share Posted February 22, 2006 It's a broad ranging process. It's involved in the eutrophication process, and is well quantified. Layton I'm sure it was quantified. What I said was I would like to see that. Otherwise it's too vague we don't know how much effect it would have in an aquarium. But I agree there is likely an effect, but the important question is how much effect, in an aquarium? IE, if the effect is negligeable, then why worry? Quote Link to comment Share on other sites More sharing options...
Feelers Posted February 22, 2006 Report Share Posted February 22, 2006 Personally, I think that a sand bed will fill up, and become a "septic tank" as layton says. If organic gunk is landing on surely it will sink down into it. However, if it does leech PO4, the amount doesnt seem to be un-managable. If you have a good skimmer surely it just skims out whats being released, and you have the other benefits of a sand bed. Otherwise Pies tank would have loads of PO4 problems, and surely his sand bed is old enough to be "full"? All the tanks that crashed - did anyone do a phospahte test(out of interest)? Oooh I'm now a 3 star citizen! :lol: Quote Link to comment Share on other sites More sharing options...
wasp Posted February 22, 2006 Report Share Posted February 22, 2006 All the tanks that crashed - did anyone do a phospahte test(out of interest)? Some "crashes" are caused by overheating or similar disasters, but generally what people refer to as a "crash", is in fact a buildup of phosphate until the algae and related problems become so bad the person is forced to strip the tank & start again. Most often the sand bed will be the culprit, doing exactly what you said, holding crud and accumulating waste. However it does not have to be this way, there are ways to manage a sandbed, as evidenced by some of the long term successful sand containing tanks that exist. Quote Link to comment Share on other sites More sharing options...
Feelers Posted February 22, 2006 Report Share Posted February 22, 2006 Ohhh, I thought a crash was you come home one day and the tank is all dead or dieing. I thought it was a fast happening thing, like a sudden release of all the phospate due to some shift in the dynamics of the sand bed... or something. :oops: In that case the term "timebomb" seems a little unjustified. I dont think I'd be too scared by a new wave of Al Quaeda attacks with slow release post-accumulation expulsion devices. Wouldnt have quite the same ring to it. :lol: Quote Link to comment Share on other sites More sharing options...
wasp Posted February 22, 2006 Report Share Posted February 22, 2006 It can be fast(ish), normally with DSB's, there may be some change in the sandbed either known about or not so obvious, that can lead to a release of nasties and cause mayhem in the tank in just a few days. But these events where much more common years ago when other technology such as skimmers were less advanced. An old school of thought was to have a DSB, and no skimmer, and not even much flow. The DSB was supposed to take care of all the waste. But this approach was highly likely to cause problems eventually. Quote Link to comment Share on other sites More sharing options...
lduncan Posted February 23, 2006 Report Share Posted February 23, 2006 The DSB was supposed to take care of all the waste. But this approach was highly likely to cause problems eventually. I wonder why that was? Maybe the sand doesn't convert all the "badness" into "goodness". Maybe it does behave the same as sand in nature does. The only difference is that it's in a glass box, with a lot less water to buffer any effects, and with a lot more input of phosphate. If you're interested. Walter Adey was a massive proponent of natural DSB type systems. It doesn't take much to find that even this self expert on such systems couldn't make them work different to what they do in nature. He has a string of public failures after his name. The Smithsonian, the GBR aquarium, and a few others, all setup, and some maintained by him. He still couldn't get the sand to stop cycling nutrients like it does in nature. His couldn't keep sps corals alive, and had serious algae problems. Layton Quote Link to comment Share on other sites More sharing options...
Pies Posted February 23, 2006 Report Share Posted February 23, 2006 Maybee he should have given me a call, my SPS are doing great. Pie Quote Link to comment Share on other sites More sharing options...
lduncan Posted February 23, 2006 Report Share Posted February 23, 2006 Maybee he should have given me a call, my SPS are doing great. Pie Hey Pies, have you died before? You do know that people die at some point, don't you? Or do you think death doesn't apply to you because you've never actually died before? Layton Quote Link to comment Share on other sites More sharing options...
lduncan Posted February 23, 2006 Report Share Posted February 23, 2006 Vague is right. Maybee if you argue it long enough it will become true... Nothing vaugue about it. It's saying if you have a sediment, with oxygen gradients within it, you get storage of phosphate by the bacteria which reduce nitrate. "Microorganisms involved in this process are capable of phosphate uptake in excess of their metabolic requirements and store phosphate internally as polyphosphate (polyP) polymers." And that release of this stored phosphate is triggered by a number of different events, ultimately causing suboxic boundary moving closer to the sediment / water boundary. Now, in a tank you have a sediment (sand bed) and you have bacteria. The question is, is for this process to NOT occur, you have to somehow stop the bacteria grabbing the phosphate. How do you do this? You have no control over it. One of the benefits of DSB's are that they reduce nitrate. If they are doing this, they are also storing phosphate, for later release. So, how does this NOT apply when you move the sand from the ocean into a glass box, where water volumes relative to sand area are much lower, and phosphate input per unit volume is much higher? Layton Quote Link to comment Share on other sites More sharing options...
lduncan Posted February 23, 2006 Report Share Posted February 23, 2006 However it does not have to be this way, there are ways to manage a sandbed, as evidenced by some of the long term successful sand containing tanks that exist. How? Quote Link to comment Share on other sites More sharing options...
Pies Posted February 23, 2006 Report Share Posted February 23, 2006 Hey Pies, have you died before? You do know that people die at some point, don't you? Or do you think death doesn't apply to you because you've never actually died before? Ummmmm ok... The bottom line is you think you know how sand beds work, hence the logic you apply to these 'clever' little analogys. The reality is your wrong, and you can link a zillion pages to web-sites and your so called expert sources, no-one is listening, and arguing with you is pointless, because you won't listen. DSB work, all the theory in the world doesn't disprove the fact that superior results for reef tanks, SPS included, can and are common with systems using a DSB. Nothing you say, no matter how many posts you make or links you provide are going to change this, it is a fact, just because you don't like it or don't agree with it won't change it. Its about as convincing as trying to proove to us that the earth is still flat. Pie Quote Link to comment Share on other sites More sharing options...
lduncan Posted February 23, 2006 Report Share Posted February 23, 2006 If the sources I've provided are wrong, what's goes on in the sand in your tank? Where does the nitrate go and how? What happens to phosphate? What happens to metals like iron, copper, manganese? What happens to sulfate? Layton Quote Link to comment Share on other sites More sharing options...
jetskisteve Posted February 23, 2006 Report Share Posted February 23, 2006 Isnt their an unwritten rule about posting one post after another without replies Quote Link to comment Share on other sites More sharing options...
wasp Posted February 23, 2006 Report Share Posted February 23, 2006 Come on Layton, I know you already know that stuff. What happens to nitrate? Maybe it gets turned into nitrogen gas, something a DSB does very well. What happens to phosphate? Maybe it is used by bacteria & single celled algae & is then skimmed. What happens to metals like iron, copper, manganese? Maybe they get eaten by some of your metal eating bacteria. What happens to sulphate? Maybe a lot of different things can happen to sulphate, it's not going to be a worry. Quote Link to comment Share on other sites More sharing options...
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