What’s your opinion on the role of detritus in a reef tank

2Wheelsonly

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Read several of the posts, but to answer the OP, I'm a fan of it. It's simply amazing we can keep pieces of the ocean alive in our living rooms. Nature adapts. The particle size, composition, breakdown and use of every atom in a reef tank can be debated ad nauseum. Bottom line, we are trying to recreate a natural reef which is a very dirty place. Anyone that has ever swam through a reef has a dirty crevice or two to support this fact.
The biggest difference is the magnitude of the enclosure. In reality, the ocean is an endless supply of nutrients in and out; those currents are ensuring new water is hitting those corals 24/7. Our tanks are recirculating the same water over and over again until we do water changes and of course supplement the water.
 
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shaggydoo

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The biggest difference is the magnitude of the enclosure. In reality, the ocean is an endless supply of nutrients in and out; those currents are ensuring new water is hitting those corals 24/7. Our tanks are recirculating the same water over and over again until we do water changes and of course supplement the water.
Exactly my point. The magnitude of the difference between natural oceans and even the largest tank shows how little we can control. The best salt mix and testing in the world won't compare to the stability offered by the mildest ocean current.

In the end, we are trying to replicate nature, which is dirty and why I'm pro detritus. If you can replicate the endless supply of in/out supply of the ocean and scale it down accurately into even a 50,000 g tank (that still pales in comparison to the size of an ocean), you can then claim to be in control. Until then, we have to sit back in amazement at the ability of nature to adapt and realize we are not in control. At that point, let nature, in all its dirty glory, run your tank.
 

Michelle Crossley

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I love the appearance of a nice, clean, bed of sand. I love that they reflect light and seem to add more visual interest to systems. I have never had fish or shrimp that utilize sand, so I'm not missing out there, but it was always fun watching Nassarius spp. appear from the sand when they sensed food enter the water. The only issue that I had with sand was that I often became too lazy to maintain it to a level that wouldn't cause my display to look impossibly disgusting when the sand was stirred. :(


Thank you! I appreciate that. :)
Why am I getting unsightly brown stuff on my sand.?
 
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Phildago

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Detritus is the best if left undisturbed. By definition detritus is inert, but it's the perfect medium for biological filtration and typically builds up where waste accumulates. The more you have the better your ratio of waste to detritus, and the more surface area you will have exposed to hungry mouths living in/on detritus.

I guess it's possible that metals and unwanted left over matter could be slowly dissolved into our water from detritus, but I doubt it's anything water changes can't handle
 

sbdiehl88

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In my humble opinion CUC does nothing for detritus. Whatever they eat they either poop back out or convert to body mass which is then released again when they die. CUC is for stirring the sandbed, and converting algae into detritus that can then be consumed by corals. Good flow keeps it in suspension long enough for corals to eat it. Once it breaks down into chemicals the ATS gets it. I have more trouble maintaining enough nutrients to keep dinos at bay. Just my 2 cents.
 

Nano sapiens

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Dan_P

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I run dual filter socks along with floss inside the baffle between the middle compartment and return and still get detritus build up in all three compartments and of course LOTS in the tank and overflows. I only feed once per day and feed LRS food with a baster just putting enough in at a time to get consumed in controlled bursts every 30 seconds until all food is gone for the day. Even with 100x turnover inside the tank the detritus builds up and there is a lot that never even makes it to the sump to be filtered out.
What color is this detritus? Do you remove for cosmetic reasons?
 

Dan_P

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I'm going to stick my little toe into these muddy waters :)

In these detritus discussions, I've noticed the tendency to laser-focus in on what the material is composed of. This is all fine and good, but I believe that it's been rather well established that the good majority of the detritus (aka 'Mulm') is primarily composed of material that has gone through many digestive processes to the point that it's very nearly inert.

So, examining detritus from a purely physical aspect might just throw some light on this subject. Taking an extreme example, what happens when a reef aquarium sand bed is effectively clogged with detritus and bioturbidation is essentially non-existent? What processes that would normally take place in a healthy, friable sand bed are effected? Off the top of my head, the obvious one is that oxygen that would normally enter the sand bed via advective flow is much reduced. It follows that nitrification via bacteria (which use oxygen) would be severely reduced and therefore denitrification would also be reduced since the nitrate needed by these bacteria would be minimally available to them in the mostly anaerobic layers of the clogged sediment. The net effect would theoretically be an increase in ammonia and nitrate (unless the system has some other effective way of dealing with these). This and other possible side effects from such a severely clogged substrate would undoubtedly have a negative effect on the health of a system.

I came across this article tonight and had one of those 'Wow, that's pertinent and interesting!' moments.

Sciencedirect - Bioturbidation

'Marine benthic habitats of the late Neoproterozoic and early Phanerozoic (600–500 Ma) were very different from benthic habitats that existed later. Seafloors at this time were characterized by well-developed microbial mats, as suggested by studies of sedimentary fabric preserved in the geologic record. These extensive microbial mats and associated seafloor fauna, such as immobile suspension-feeding helicopacoid echinoderms, became scarce or extinct in the Cambrian. The substantial change that occurred in seafloor communities around this time, termed the ‘Cambrian substrate revolution’, is thought to be caused by the development of bioturbation. It is hypothesized that the emergence of both bioturbation and predation around this time led to the extinction of nonburrowing taxa and influenced subsequent development of animal body plans during the Cambrian. Bioturbation also made a new food resource, buried organic matter, accessible to deposit feeders while radically changing the geochemistry of the seafloor.'

Hmm, that 'extensive microbial mats' line sounds a lot like the cyano mats that we run into when a substrate doesn't have the organisms that would keep it friable (aka: 'bioturbidation organisms') and/or the helping hand of the aquarist with a stick or a hose/vac.

Perhaps Delbeek and Sprung (Reef Aquarium, Vol 3) said it best:

"The conditioning of a healthy aquarium involves a certain amount of detritus accumulation that promotes a healthy diversity of life within the substrata. Later on, this accumulation can become excessive, but in this chapter, we have outlined ways to prevent this."
@Nano sapiens, your post stimulated this viewpoint:

Detritus that concerns you might just be mulm, the equivalent of metabolic ash
Mulm seems to have a very low density, maybe a milligram in 10 ml of “fluff”
Mulm is unattractive, but harmless material
The exact mechanism for a substrate to become “clogged” has not been described. Does solid matter, such as mulm, somehow intrude into the spaces of sand, or more likely, does in situ generation of mulm accumulate until the sand becomes inhabitable?
Removal of the accumulated mulm in the substrate with bioturbation or by rip cleaning, stirring or vacuuming are ways to keep the substate habitable.
 

Nano sapiens

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@Nano sapiens, your post stimulated this viewpoint:

Detritus that concerns you might just be mulm, the equivalent of metabolic ash
Mulm seems to have a very low density, maybe a milligram in 10 ml of “fluff”
Mulm is unattractive, but harmless material
The exact mechanism for a substrate to become “clogged” has not been described. Does solid matter, such as mulm, somehow intrude into the spaces of sand, or more likely, does in situ generation of mulm accumulate until the sand becomes inhabitable?
Removal of the accumulated mulm in the substrate with bioturbation or by rip cleaning, stirring or vacuuming are ways to keep the substate habitable.
As I see it, detritus or mulm are just catchalls for any small particulate material in an aquarium that results from biological processes. Some, such as organic material that has been mineralized is relatively dense. Some of it is more 'fluffy'. Some is in between.

Detritus is actively deposited in the sand bed via the advection process. This is the main physical process (diffusion is the other, but occurs where water flow is very slow and is a relatively slow process) that leads to a 'clogged substrate'. Unless this material is somehow removed, it will accumulate as long as pore space between the sand grains is available.

Delbeek and Sprung have a few pages devoted to the topic (The Reef Aquarium, Vol 3).

"The flow of water into the substratum by advection also results in the transport of particles and dissolved substances from the water column into the substratum. Detritus, phytoplankton, zooplankton and dissolved and particulate matter all enter sand, gravel, or rocks by this process."
 

2Wheelsonly

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What color is this detritus? Do you remove for cosmetic reasons?
Fresher detritus is usually brown in color and the older stuff that collects in my rocks is grey. I remove it because it really starts to pile up and if I ever am blowing my rocks off I can create one heck of a dust cloud in the water. I try to avoid letting it get that bad but the more corals grow the harder it is to reach spots in the rock where it piles up.
 
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So can we just call the gray stuff “gray matter”? Basically it’s not detritus but useless leftovers after everything has had a bite at it? Guess I should siphon some out.
 

Hemmdog

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I mainly leave my sand alone. I used to have a goldhead sleeper goby that would take care of it for me. Now I just vacuum it once a quarter. Very satisfying and scary how much yuck comes up. The tanks seem mad for a few days after I do that. Maybe I should stop doing that. Not sure. My 40b bare bottom gets a lot of detritus accumulation but I believe that is from inadequate flow to the whole tank. There’s always mulm mountain in my back right corner. ;Muted

I don’t run filter socks on any of my systems btw.
 

plankton

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Whenever I cleaned my filter bags on my old 210G when I had it they were teaming with pods cuz that was a safe environment and that’s were the food was! I’d collect the pods and introduce some back to refugium and some back to DT. Oh man did fish and corals respond well to live copepods.

So ‘live’ detritus as food for pods etc is very good. Dead detritus that is just decomposing is not so good.
 

Dan_P

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Fresher detritus is usually brown in color and the older stuff that collects in my rocks is grey. I remove it because it really starts to pile up and if I ever am blowing my rocks off I can create one heck of a dust cloud in the water. I try to avoid letting it get that bad but the more corals grow the harder it is to reach spots in the rock where it piles up.
i wonder if fish only systems have the same production rate of detritus?
 

brandon429

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@Dan_P
something you said had a delayed effect on me


we do need correct terminology you’re right, the word detritus to me means risk, doom on the verge, feeds invasions. negativity, due to inviting random sandbed challenges online we see the anoxic forms by selection it seems

but to someone who has never needed to disassembly clean/strip all sandbed heterogeneity as a side effect goal of removing all waste, detritus is helpful marine snow

what follows in typical discussion is the semantics clash train wreck that comprises most sandbed pro / con threads


what truly is a helpful term to separate safe zone waste from risk-zone waste?

Lasse has always offered a fair and balanced view of the helpful forms and he likes to call it particulate organic waste, likely from aquaculture industry references
 
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Dan_P

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@Dan_P
something you said had a delayed effect on me


we do need correct terminology you’re right, the word detritus to me means risk, doom on the verge, feeds invasions. negativity, due to inviting random sandbed challenges online we see the anoxic forms by selection it seems

but to someone who has never needed to disassembly clean/strip all sandbed heterogeneity as a side effect goal of removing all waste, detritus is helpful marine snow

what follows in typical discussion is the semantics clash train wreck that comprises most sandbed pro / con threads


what truly is a helpful term to separate safe zone waste from risk-zone waste?

Lasse has always offered a fair and balanced view of the helpful forms and he likes to call it particulate organic waste, likely from aquaculture industry references
@brandon429, @Lasse is worth listening to :). Here are some thoughts.

Particulate organic waste sounds like something that could be measured. I saw a table in Ken Feldman’s total organic carbon article. I seem to recall that particulate organic carbon, material removed by a 0.2 micron filter, accounts for roughly 10% of the total organic carbon in various ocean environments. I wonder whether it is much higher in an aquarium? And if you had a choice, would you prefer a higher or lower ratio of particulate to dissolved organic matter?

Coming back to sand bed pro-con debates, we still do not have a simple method to measure sand bed health, probably for two reasons. We never got around to defining a healthy substrate. If you cannot describe what ”good” looks like, describing the measurable characteristics is impossible. We might define a rip cleaned substrate as “good”. I would add that washed new sand is probably too sterile to be considered good or ideal. We might use chemical oxygen demand or substrate biological oxygen demand (@taricha has been poking around this topic) as diagnostic measurements. This would directly address the risk of a sand bed going bad or causing problems, and remove the need to worry about visible detritus.

My research time and budget has been heavily weighted towards understanding cyanobacteria nutrition. This has taken me on quite a number of side trips and visits down rabbit holes. The next side trip is the role of substrate and cyanobacteria growth. I mention this because the study may turn up interesting things about sand beds that apply to this discussion.

I leave you with the question, what is a healthy substrate.
 

fish farmer

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@brandon429, @Lasse is worth listening to :). Here are some thoughts.

Particulate organic waste sounds like something that could be measured. I saw a table in Ken Feldman’s total organic carbon article. I seem to recall that particulate organic carbon, material removed by a 0.2 micron filter, accounts for roughly 10% of the total organic carbon in various ocean environments. I wonder whether it is much higher in an aquarium? And if you had a choice, would you prefer a higher or lower ratio of particulate to dissolved organic matter?

Coming back to sand bed pro-con debates, we still do not have a simple method to measure sand bed health, probably for two reasons. We never got around to defining a healthy substrate. If you cannot describe what ”good” looks like, describing the measurable characteristics is impossible. We might define a rip cleaned substrate as “good”. I would add that washed new sand is probably too sterile to be considered good or ideal. We might use chemical oxygen demand or substrate biological oxygen demand (@taricha has been poking around this topic) as diagnostic measurements. This would directly address the risk of a sand bed going bad or causing problems, and remove the need to worry about visible detritus.

My research time and budget has been heavily weighted towards understanding cyanobacteria nutrition. This has taken me on quite a number of side trips and visits down rabbit holes. The next side trip is the role of substrate and cyanobacteria growth. I mention this because the study may turn up interesting things about sand beds that apply to this discussion.

I leave you with the question, what is a healthy substrate.
Back in the day Ron Shimek had an article about sand bed health with regards to the sand bed fauna and ways to measure said fauna.

A normal sand bed was supposed to have 10,000 to 100,000 animals per meter square. mediocre sand bed fauna would range 1,000 to 5,000 animals per meter squared, this would be time for a "recharge kit" or new live sand. Anything below 1,000 animals per meter squared he recommended tearing down and rebuilding.

Granted this info is 20 years old and was based on Ron Shimek's definition of a DSB at the time.

He also recommended checking your sand bed fauna every few months.
 

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