Substrate Vacuuming. An Analysis

[Dan_P]

I have often wondered how much material (is it all detritus?) is removed from a substrate when it is vacuumed. I am moving the contents of a 40 gallon aquarium to a 75 gallon aquarium and some or all of the sand is going. I am taking the opportunity for a small substrate study and I am looking for any comments or ideas on the approach.

The system is a four year old fish only aquarium with 1-2 inches of fine silica sand when spread evenly, but now there are some sand dunes 2-3 inches deep and some bare spots. In today’s substrate survey, I vacuumed up sand along with tank water. I let the sand settle and poured off the water. The sand slurry was poured into a graduated cylinder and allowed to settle. The volume of sand was 77 mL, representing a roughly 2 by 2 by 1 inch deep volume of substrate. The water was centrifuged, leaving a very dark pellet of sludge, about 1.3 mL in volume. Under the microscope, the sludge consisted mostly of amorphous and translucent looking material with only a scattering of recognizable forms.

On a volume basis, the sludge makes up around 2% of the substrate volume. I have no reference to say whether this is good, bad or a so-what. I do wonder if the above approach might be a way to characterize the condition of a substrate. A new substrate might have no sludge, a one year old substrate a little, a vacuumed substrate might have another level. Does the amount of sludge level off after some time? Can sludge accumulate indefinitely or is there a physical limit? Does the amount of sludge reach a steady state in a healthy system?

Dan

 

[cojo8888]

Very interesting following the post so basically vacuuming sand dosent really contribute lot on managing detritus? 2% is really low for number

 

[Dan_P]

Very interesting following the post so basically vacuuming sand dosent really contribute lot on managing detritus? 2% is really low for number

2% does seem too low to worry about.

I need to think about how much material 2% represents for the entire substrate. Maybe that is an impressive number.

 

[ca1ore]

Also consider whether ‘sludge’ is even problematic, regardless of how much is there. If it’s already mineralized mulm then it’s essentially just mud.

 

[KrisReef]

It might be interesting to add the sludge back into some "clean" seawater and do comparison water tests between the clean seawater and seawater plus sludge too see what the sludge might contribute (leach) into the clean water.

 

[Dan_P]

It might be interesting to add the sludge back into some "clean" seawater and do comparison water tests between the clean seawater and seawater plus sludge too see what the sludge might contribute (leach) into the clean water.

I did a PO4 test of the centrifuged water (sludge removed) and PO4 was greater than tank water. I am going to repeat this to confirm this was PO4 from the substrate.

 

[Dan_P]

Two more substrate surveys today (vacuuming the sand and centrifuging the material suspended in the water, one shallow and one deep substrate) for a total of 170 mL of substate removed and 1.8 mL of sludge recovered. The sludge amount on a volume basis is 1.1% of the substrate, about half of what was found in the first survey. In addition, with the aid of a a magnifying glass, the centrifuge pellet appeared to be made up of half sand and half mud. This characterization is very rough but points to the sludge content as being possibly lower than 1% of the substrate volume (I froze the sludge sample for possible further analysis).

A possibly more interesting observation was that the water sample from the vacuuming process had a PO4 concentration of 0.29 ppm while the tank water concentration was 0.03 ppm. This translates to 19 mg of PO4 in 170 mL of substrate or if all the substrate in the tank was thoroughly stirred up in the tank, the phosphate level would jump to 1 ppm. Previous tests of pore water showed elevated PO4 levels but never high enough to come close to raising the tank PO4 level to 1 ppm. Also, the amount of pore water in the substrate is only a fraction of 2 gallons. The substrate seems to contain a reservoir of phosphate that is locked up somehow.

Ammonia, or at least a positive test result, was also found in the water sample. Ammonia had been detected in pore water previously.

Having never vacuumed the sand bed (fine silica sand) in the last four years of heavy feeding, these results seem to indicate that vacuuming might be beneficial for removing phosphate, but might also accidentally release phosphate and ammonia. I have no idea what impact vacuuming would have on the biofilter when exposing bacteria colonies acclimated to low oxygen levels suddenly to higher oxygen levels.

 

[427HISS]

Dan, very interesting last results. Also what it would do to the biofilter.
Great job, so keep going.

 

[brandon429]

Oh wow

This is done so well I don’t recall such testing before this thread is really worth more review

How about I link it to some really heavy detritus debates, we asked for testing there and nobody did it

Can you nitrate test the mud water

After it sits hydrated and unstratified/aerated then it’s nitrate potential should really be remarkable

I’ll get to linking. This is on the last page of my sand rinse thread now.

 

[brandon429]

https://www.reef2reef.com/threads/w...ltration-the-brs-wwc-system-ep7-brstv.487552/

They need to see your work there. It’s not that detritus is bad, it’s not, it’s that it must be factored as bioloading and it’s not neutral as soon as dilution starts to reduce or as de stratifying events occur.

Actual nutrient testing of detritus is rare and thank you for doing this. Berlin method and ten million proponents said detritus was mineralized over time. we could tell it wasn’t going neutral by the manifestations in invasion challenge threads but I’d never seen a chemical reading. Do skimmate!

I’d be curious to know nitrite readings too off a fresh dredge test from lower layer sand. Thanks tons for posting.

 

[KrisReef]

Two more substrate surveys today (vacuuming the sand and centrifuging the material suspended in the water, one shallow and one deep substrate) for a total of 170 mL of substate removed and 1.8 mL of sludge recovered. The sludge amount on a volume basis is 1.1% of the substrate, about half of what was found in the first survey. In addition, with the aid of a a magnifying glass, the centrifuge pellet appeared to be made up of half sand and half mud. This characterization is very rough but points to the sludge content as being possibly lower than 1% of the substrate volume (I froze the sludge sample for possible further analysis).

A possibly more interesting observation was that the water sample from the vacuuming process had a PO4 concentration of 0.29 ppm while the tank water concentration was 0.03 ppm. This translates to 19 mg of PO4 in 170 mL of substrate or if all the substrate in the tank was thoroughly stirred up in the tank, the phosphate level would jump to 1 ppm. Previous tests of pore water showed elevated PO4 levels but never high enough to come close to raising the tank PO4 level to 1 ppm. Also, the amount of pore water in the substrate is only a fraction of 2 gallons. The substrate seems to contain a reservoir of phosphate that is locked up somehow.

Ammonia, or at least a positive test result, was also found in the water sample. Ammonia had been detected in pore water previously.

Having never vacuumed the sand bed (fine silica sand) in the last four years of heavy feeding, these results seem to indicate that vacuuming might be beneficial for removing phosphate, but might also accidentally release phosphate and ammonia. I have no idea what impact vacuuming would have on the biofilter when exposing bacteria colonies acclimated to low oxygen levels suddenly to higher oxygen levels.

Thanks for posting these results.
That is a very interesting level of phosphate showing up in your tanks wastewater.
Do you happen to measure Calcium, Magnesium, pH, and Kh in this system?

 

[Dan_P]

Dan, very interesting last results. Also what it would do to the biofilter.
Great job, so keep going.

Your last notion got me thinking about testing the substrate. The first step would be sampling the substrate, “feeding” it and noting how quickly it consumes nitrogen and carbon under very low flow. Then increasing the flow to suspend the substrate and note whether this disrupts feeding rate. Finally, return to low flow and note how long it take for substrate to return to its initial level of activity.

 

[Dan_P]

Thanks for posting these results.
That is a very interesting level of phosphate showing up in your tanks wastewater.
Do you happen to measure Calcium, Magnesium, pH, and Kh in this system?

Yes, I measure all parameters weekly except pH. I have very good records back through 2017, encompassing before and during acetate dosing. I have not reported on this multi-year observation yet.

What is your question?

 

[Dan_P]

Oh wow

This is done so well I don’t recall such testing before this thread is really worth more review

How about I link it to some really heavy detritus debates, we asked for testing there and nobody did it

Can you nitrate test the mud water

After it sits hydrated and unstratified/aerated then it’s nitrate potential should really be remarkable

I’ll get to linking. This is on the last page of my sand rinse thread now.

Link away.

No nitrate detected, but ammonia was detected.

I have done aeration studies of tank water and was surprised at how much ammonia and nitrate are generated over several weeks, showing the potential for 0 ppm nitrate and 0 ppm phosphate to harbor material that can be converted to several ppm of N. This data can be compared to the levels produced during aeration of a mud suspension. This will take some weeks. I started an exploratory study, aerating the supernatant of the sand-water mixture from the vacuuming.

 

[Dan_P]

Do skimmate

In progress. I have completed a survey focused on demonstrating that high skimmate rates (wet skimming) remove more material than slow rates (dryer skimming). I can share these results. I am planning the next study, this time including a “poor man’s” test for organics and tighter experimental controls.

 

[brandon429]

It is so far unacceptable that this thread fall to page 2. It's not earth shattering to know detritus has some waste, but it sure doesn't fit lots of claims regarding DSB function.

I was told DSBs mineralize detritus and the years yours had to work didn't seem to. Ammonia sourcing implies bed exchange with water column though the materials always stated the grains would cause stratification that locks in areas of 'benefit'


How rare is it to have strong laboratory technique, measure and gear access to test core claims in reefing

The work so far shows as well some nutrient value and ratios certain reefers may plan for, marine snow balances, where detritus stores might be made on purpose to mimic higher nutrient zones in nature. Cryptic filters or zones love the material...dendros probably do... It's just good to have a measure for once, something pinpointed. Can't wait to see nitrogen potential, watching for patterns similar to hundreds and hundreds of BOD samples our crew had to run in cattle rendering runoff waste ponds which sets the overall speed one can run a cattle processing plant the size of a small town.

We measured detritus' version of Godzilla. Can't wait to see the reef tank breakdown in percentages... How nitrogen species express after given good aeration for two days after a mud sample. People ought to mail you a few samples of reef detritus, nutrient ratio comparisons and link the tank pics the samples come from.

 

[KrisReef]

Yes, I measure all parameters weekly except pH. I have very good records back through 2017, encompassing before and during acetate dosing. I have not reported on this multi-year observation yet.

What is your question?

Ultimately,I am wondering about Kh levels and precipitation of phosphate in your substrate.
I’ll wait eagerly until you publish the rest of the story.

 

[Dan_P]

Ultimately,I am wondering about Kh levels and precipitation of phosphate in your substrate.
I’ll wait eagerly until you publish the rest of the story.

I measured the alkalinity of pore water and it wasn’t much different from tank water, if I remeber correctly slightly higher. PO4 can also adsorb to organic particles which might be the reason I measure elevated PO4 in skimmate. Lot to learn.

 

[Dan_P]

Today’s substrate survey was performed differently. Instead of vacuuming, I used a small beaker to carefully scoop out the substate (sulfur odor more noticeable today because I was plowing a sand dune. . Collected 500 mL of sand. Centrifuged the rinse water (2200 mL) to obtain two pellets. A 1 mL pellet was obtained from the water after the heavier sludge settled for an hour while I went to vote and a 6 mL pellet consisting of the heavier precipitate. The supernatant had a light yellow color like skimmate. The pellet volume was 1.4% of the substrate volume. I think that’s all the substrate that I will disturb until I analyze what I collected so far.

Don’t forget that I have silica sand or maybe more like granite sand. Aragonite sand might behave differently, collecting more or less material. Aragonite is known to adsorb in addition to PO4, organics more strongly than silica sand.

 

[brandon429]

Can someone tell me if these ammonia levels are what I should be shooting for?

www.reef2reef.com

kick up a great thread here. Im adding this one in the link bc they've tested skimmate, Im sure many have but at least it relates to waste analysis and some of this skimmate eventually is bound to become detritus at least in some portion, through some possible pathway....testing the nutrient levels of things we remove in the hobby is helpful science