What’s In Your Substrate?

[Dan_P]

After several conversations with @taricha and @brandon429, I became interested in measuring the amount of organic material in the substrate of my fish only system. One method I found uses basic KMnO4 to estimate the chemical oxygen demand (COD) in a sample. The amount of KMnO4 consumed correlates to total organic carbon (TOC) present. I have just started to play around with this method and haven’t done anything serious about validating it or comparing the KMnO4 consumed to the TOC value from a Triton N-DOC test. I can hear @Rick Mathew tsk tsk’ing now What I did first was to look at the material that shakes loose from aquarium substrate. Here is the experiment.

I very gently scooped 20 mL of substrate from the aquarium, being careful to avoid losing anything. I dipped down about an inch which gave me a mixture of surface substrate and some deeper material. I can already see that a standard sampling is needed. I transferred the sand to a stoppered flask and very gently swirled it with 32 mL of tank water for 15 seconds, making sure I turned over all the substrate to free all the loose material. I followed this with 3-30 second very vigorous shakings. I measured the COD of the wash water after each wash. The plot below shows the cumulative COD. I also photographed the wash sample for the first three washes.

Observations and thoughts. The total change in absorbance 0.27 is 10x higher than the value for just aquarium water. This is more impressive when you consider that this amount of material being concentrated in the substrate and adjacent to a small amount of pore water. Quite a soup!

My first gentle wash is a model of substrate vacuuming. I tried to duplicate the turbulence I remember seeimg when I used to vacuum substrate. If I got this right, and I am way out on a limb here, vacuuming removes half the organic material. It takes very, very turbulent mixing to remove more material. I did not figure a good way to measure everything adhered to the substrate so I could determine when the washing was near completion. The measurement probably reflects a digestion of organisms (sorry guys) and organic matter In the substrate.

I would be interested in your thoughts that came to mind when you read this post.

Dan

 

[Rick Mathew]

After several conversations with @taricha and @brandon429, I became interested in measuring the amount of organic material in the substrate of my fish only system. One method I found uses basic KMnO4 to estimate the chemical oxygen demand (COD) in a sample. The amount of KMnO4 consumed correlates to total organic carbon (TOC) present. I have just started to play around with this method and haven’t done anything serious about validating it or comparing the KMnO4 consumed to the TOC value from a Triton N-DOC test. I can hear @Rick Mathew tsk tsk’ing now What I did first was to look at the material that shakes loose from aquarium substrate. Here is the experiment.

I very gently scooped 20 mL of substrate from the aquarium, being careful to avoid losing anything. I dipped down about an inch which gave me a mixture of surface substrate and some deeper material. I can already see that a standard sampling is needed. I transferred the sand to a stoppered flask and very gently swirled it with 32 mL of tank water for 15 seconds, making sure I turned over all the substrate to free all the loose material. I followed this with 3-30 second very vigorous shakings. I measured the COD of the wash water after each wash. The plot below shows the cumulative COD. I also photographed the wash sample for the first three washes.

Observations and thoughts. The total change in absorbance 0.27 is 10x higher than the value for just aquarium water. This is more impressive when you consider that this amount of material being concentrated in the substrate and adjacent to a small amount of pore water. Quite a soup!

My first gentle wash is a model of substrate vacuuming. I tried to duplicate the turbulence I remember seeimg when I used to vacuum substrate. If I got this right, and I am way out on a limb here, vacuuming removes half the organic material. It takes very, very turbulent mixing to remove more material. I did not figure a good way to measure everything adhered to the substrate so I could determine when the washing was near completion. The measurement probably reflects a digestion of organisms (sorry guys) and organic matter In the substrate.

I would be interested in your thoughts that came to mind when you read this post.

Dan

No tsk tsking here...just great admiration for you good work...Excellent EXPERIMENT

 

[brandon429]

Dan can you define that one value for me on the left, the abs value, and to guide chart interpretation does that above state that within 4 washings of a given sample the value for oxygen demand in the sample water increases

are there more organics liberated with each session of shaking/ so the oxygen demand increases vs just tank water alone?

 

[Randy Holmes-Farley]

Organic material in such a test would include whole living microorganisms, right? Bacteria, etc?

 

[Dan_P]

Dan can you define that one value for me on the left, the abs value, and to guide chart interpretation does that above state that within 4 washings of a given sample the value for oxygen demand in the sample water increases

are there more organics liberated with each session of shaking/ so the oxygen demand increases vs just tank water alone?

“Abs” refers to the change in absorbance of the pink KMnO4 solution. In this case, things are bit backwards. As the amount of organics increase, the concentration of KMnO4 decreases, the solution becomes less pink, and the absorbance declines. The amount of the decline in pinkness or absorbance relates to the amount of organics. A better label for the y-axis would have been KMnO4 consumed.

You are correct, the longer that I agitate the water-substrate mix, the more material is suspended in the water and the larger the chemical oxygen demand. It looks like the amount of stuff shaking loose is reaching an end point for my shaking technique. If I could measure the the material still adhering to the sand, we would know if the leveling of means clean sand or that I need to shake harder.

 

[Dan_P]

Organic material in such a test would include whole living microorganisms, right? Bacteria, etc?

I am assuming everything is being digested, living and nonliving matter alike. You hit on an important point. What does the COD value convey?

If what is being digested is bacteria, then maybe my substrate is not dirty. If what is being digested is non-living matter, my substrate contains waste. But if the waste is there because bacteria can’t digest it, its not a source of nitrates or phosphates but maybe its just clogging up the substrate pores.

I have been discussing these ideas with @taricha, especially the notion that the waste is ”biological ash”, not a source of nutrients just a physical mess. I am running a BOD experiment on this organic material to help resolve the ash v nutrient source debate. Maybe I need microbiome analysis of this material too.

 

[taricha]

I looked at my Biological Oxygen Demand for the grunge that washes out of 20mL of substrate vs aquarium water, but I don't think I can make a meaningful comparison to @Dan_P ' s data because although I can compare our dilutions, based on the pics I have waaaay more grunge wash out of 20mL of my sand.

So I'll be interested to see what the Chemical Oxygen Demand (oxidize everything) vs Biological Oxygen demand (bacterial activity) shows for a comparable sample.

Dan's right about much of it being the equivalent of ash. A large part of this material is a biological dead end. I experimented extensively on tubes of the stuff to see if some combination of providing or withholding C, N, P (under aerobic and anaerobic conditions) and in combination with bacterial products thought to consume this material had any effect on the amount of the material left. No difference in the physical amount of material to speak of.

I totally believe that such interventions can lower the nutrient value of the debris, but can't imagine anything can make it disappear. A @brandon429 rip clean seems to be the only option if you actually want it gone.

 

[Dan_P]

I looked at my Biological Oxygen Demand for the grunge that washes out of 20mL of substrate vs aquarium water, but I don't think I can make a meaningful comparison to @Dan_P ' s data because although I can compare our dilutions, based on the pics I have waaaay more grunge wash out of 20mL of my sand.

So I'll be interested to see what the Chemical Oxygen Demand (oxidize everything) vs Biological Oxygen demand (bacterial activity) shows for a comparable sample.

Dan's right about much of it being the equivalent of ash. A large part of this material is a biological dead end. I experimented extensively on tubes of the stuff to see if some combination of providing or withholding C, N, P (under aerobic and anaerobic conditions) and in combination with bacterial products thought to consume this material had any effect on the amount of the material left. No difference in the physical amount of material to speak of.

I totally believe that such interventions can lower the nutrient value of the debris, but can't imagine anything can make it disappear. A @brandon429 rip clean seems to be the only option if you actually want it gone.

You gave me an idea or question to answer. Is the cloudy solution of substrate washings a good culture medium for growing cyanobacteria, dinoflagellates and diatoms?

 

[taricha]

You gave me an idea or question to answer. Is the cloudy solution of substrate washings a good culture medium for growing cyanobacteria, dinoflagellates and diatoms?

In my tank, it is. At least grunge taken from around cyano areas, then held in dark (BOD protocol) for a week or so, then exposed to light and seeded with bits of cyano, it grows decent amounts of red cyano.

 

[brandon429]

Can any of the extracts be shown to be contributors to people’s nitrate reading issues, are they stores of waste that replenish water change / dissolved exports or do they appear as non contributors to nitrate stores

 

[Dan_P]

Can any of the extracts be shown to be contributors to people’s nitrate reading issues, are they stores of waste that replenish water change / dissolved exports or do they appear as non contributors to nitrate stores

Great question. My first experiment is a BOD test to determine if the extract supports aerobic bacteria growth. I will look at the BOD sample for signs of ammonia and nitrate production.

 

[brandon429]

Your thread has strong relation to this one

QUESTION OF THE DAY - If you don't do this will it CRASH your tank?

Yes, if you have enough critters ie nassarius snails, pistol shrimp and partner, goby watchman, then it helps a lot, I only clean the sand around the front and sides of the tank weekly with a long handle plastic rake and work the bottom sand upwards to the surface so it always looks clean...

www.reef2reef.com

If the detritus is inert in measure, nitrogen contribution, it will be amazing since we have changed major direction in reefing due to the stuff. It's great when science throws a 180 loop though, I hope it tests as clean as a whistle so we have to keep digging for a new link between detritus and it being the best substrate supporting most invasions in reefing (also inferred by removing detritus / beat an invasion work threads)

 

[Dan_P]

Your thread has strong relation to this one

QUESTION OF THE DAY - If you don't do this will it CRASH your tank?

Yes, if you have enough critters ie nassarius snails, pistol shrimp and partner, goby watchman, then it helps a lot, I only clean the sand around the front and sides of the tank weekly with a long handle plastic rake and work the bottom sand upwards to the surface so it always looks clean...

www.reef2reef.com

If the detritus is inert in measure, nitrogen contribution, it will be amazing since we have changed major direction in reefing due to the stuff. It's great when science throws a 180 loop though, I hope it tests as clean as a whistle so we have to keep digging for a new link between detritus and it being the best substrate supporting most invasions in reefing (also inferred by removing detritus / beat an invasion work threads)

Well, if there is going to be a revolution, this seems like a nice forum to start it

 

[Nano sapiens]

Your thread has strong relation to this one

QUESTION OF THE DAY - If you don't do this will it CRASH your tank?

Yes, if you have enough critters ie nassarius snails, pistol shrimp and partner, goby watchman, then it helps a lot, I only clean the sand around the front and sides of the tank weekly with a long handle plastic rake and work the bottom sand upwards to the surface so it always looks clean...

www.reef2reef.com

If the detritus is inert in measure, nitrogen contribution, it will be amazing since we have changed major direction in reefing due to the stuff. It's great when science throws a 180 loop though, I hope it tests as clean as a whistle so we have to keep digging for a new link between detritus and it being the best substrate supporting most invasions in reefing (also inferred by removing detritus / beat an invasion work threads)

My take is that if the testing shows that the detritus is largely inert, then I would posit that the change in the bacterial makeup between a mostly anoxic/anaerobic ('dirty, clogged sandbed') and a mostly aerobic ('clean, porous sandbed') is at least a significant contributor to the better system health of the latter. An overabundance of anoxic/anaerobic waste products (such as hydrogen sulfide, etc.) can't be a good thing...

 

[taricha]

If the detritus is inert in measure, nitrogen contribution, it will be amazing since we have changed major direction in reefing due to the stuff.

I'm going to tentatively suggest it's both inert ash and a driving force of nuisance growth.
What I mean is that it's maybe 99% inert ash in the sense that nothing you can do will digest or make the material disappear. But the other 1% is slow releasing organic carbon, nitrogen species, etc. and driving local nuisance growth.

maybe we'll see some more data on the question in the near future.

 

[brandon429]

Ok that makes good sense it does especially the part about reducibility. Paul B has been studying massive stores of detritus in his home tank via patterned observation over the years and tank moves and he’s on the side of it being more inert vs causative. Many people have inches of detritus piled in sump, Randy has mentioned over the years it’s not a game changing big deal as well as he has some. Those are two very oxygenated zones compared to at the bottom of a nine inch Berlin DSB so I can’t wait to see gradients and differences in states of decay from samples from less oxygenated zones for future testing

 

[taricha]

Those are two very oxygenated zones compared to at the bottom of a nine inch Berlin DSB so I can’t wait to see gradients and differences in states of decay from samples from less oxygenated zones for future testing

For the moment, I'm going to stay looking at near-surface water. There's plenty weird enough within the top 1" of my grungy sandbed to keep me scratching my head.

 

[Skynyrd Fish]

Most of the sps role models of mine are adamant about keeping the sump and tank free of detritus. They feel it does something chemically to the water. I wish I could easily pull up what I had read.

 

[ca1ore]

I'm going to tentatively suggest it's both inert ash and a driving force of nuisance growth.
What I mean is that it's maybe 99% inert ash in the sense that nothing you can do will digest or make the material disappear. But the other 1% is slow releasing organic carbon, nitrogen species, etc. and driving local nuisance growth.

That has long been my feeling. A mostly data free feeling though LOL. Excellent experiments though.

 

[ca1ore]

Most of the sps role models of mine are adamant about keeping the sump and tank free of detritus.

More correlation than causation I'd suspect. I think most reef keepers are borderline obsessed with detritus removal.