Are the risks of having a deep sandbed exaggerated?

[backbayreef]

The reason I like nitrate reduction is because I like to keep a lot of fish and I like to feed them well.

Almost all my tanks have been BB for the last 15 years. I started with undergravel filtration (remember those days?) but it created such a mess. I've tried DSB before but was also told to siphon and do regular maintenance. Well, I'm too busy (sounds like too lazy) to deal with sand hence I've been BB ever since.

Outside of DSB or not, I can tell you that stabilizing the tank with sand is a lot easier than BB. I went back to sand 18 months ago for the inverts that needed sand and things were great - even SPS was growing after 6-8 months. I've since consolidated tanks and went back to BB on the frag tank and new tank; but honestly, my BB tanks are not as stable.

With respect to N&P control - I run very high flow through the system so don't have much detritus. An oversized skimmer picks up all the nasties. With carbon dosing (vodka), my nitrate is ~5ppm. Phosphate is around 0.07ppm using LC-based products (PhosphateRx). On paper, my tank is looking great after 7-8 months. However, I still can't grow SPS yet.

Bottom line: no DSB for me since I'm lazy. I would just run high-flow BB tanks and wait for things to mature. Eventually, biome will grow in the rocks & pipes.

 

[56longroof]

Thank you Vintage Reefer. I appreciate hearing your experience with a DSB. I would certainly categorize your experience as negative and that adds validity to the risks of having a DSB.

I would call it a failure due to lack of knowledge. A DSB is not a set it and forget it approach. There are some requirements for success.

 

[backbayreef]

I would call it a failure due to lack of knowledge. A DSB is not a set it and forget it approach. There are some requirements for success.

Then why have it at all if one is just after low/zero maintenance or don’t care about aesthetic? If we’re just talking about controlling N&P, there are many other low-maintenance ways.

 

[56longroof]

Then why have it at all if one is just after low/zero maintenance or don’t care about aesthetic? If we’re just talking about controlling N&P, there are many other low-maintenance ways.

What low maintenance method that doesn't add equipment or chemicals? A DSB doesn't even require anything the first year or two. Then vacuum 25% 1-2" deep. Im still convinced if you put in a proper clean up crew and good flow vacuuming might not be necessary.

 

[mook1178]

I’m not sure how all that math works out. How is the O2 getting used up that does not itself produce nitrate? The organics that you propose are driven into the sand by fauna themselves contain N. Where is that N going?

I contend the theory is flawed. Doesn’t mean sand beds don’t lower nitrate, but I don’t see how they can do it for the reasons folks suggest.

O2 respiration does not directly create NO3, as I am sure you know. The vast majority of NO3 come from fish waste as ammonia. The vast majority of organics on the bottom are carbohydrates from dying bacteria, which is CH2O , in some form or another. Very little NO3 is actually produced in the sand bed itself. I will look through my Chem ocean books on this matter to find a better graph and data on the matter, but all it takes is the right depth and O2 levels for denitrification to setup. that depth is dependent on organics in the sediment.

The amount of Denitrification that happens is also dependent as stated how much NO3 is reaching the hypoxic areas. I do not believe a DSB will continue to denitrify a tank with constant 0ppm NO3. The main NO3 reduction is done in algae and will be used there before reaching the sand bed. The production of H2S begins where dentirification ends, usually by that point the areas of H2S production is completely annoxic and the bacteria is respiring SO4, which I also do not believe can be sustained long term in a healthy tank.

Too add the organics that the dentirifing bacteria need, comes from the bacteria dying that need O2. So as the bigger fauna stir the bed and add O2, that bacteria blooms. As that area is left alone for a long enough period of time, the O2 will reduce, O2 respirinig bacteria die, and NO3 respiring bacteria bloom using the organics from the dead bacteria. Yes there is a small amount of NO3 release from the bacteria dying, but not enough to sustain them long term. that is where the water column NO3 starts getting used.

 

[Randy Holmes-Farley Verified Community Expert]

O2 respiration does not directly create NO3, as I am sure you know. The vast majority of NO3 come from fish waste as ammonia. The vast majority of organics on the bottom are carbohydrates from dying bacteria, which is CH2O , in some form or another. Very little NO3 is actually produced in the sand bed itself. I will look through my Chem ocean books on this matter to find a better graph and data on the matter, but all it takes is the right depth and O2 levels for denitrification to setup. that depth is dependent on organics in the sediment.

The amount of Denitrification that happens is also dependent as stated how much NO3 is reaching the hypoxic areas. I do not believe a DSB will continue to denitrify a tank with constant 0ppm NO3. The main NO3 reduction is done in algae and will be used there before reaching the sand bed. The production of H2S begins where dentirification ends, usually by that point the areas of H2S production is completely annoxic and the bacteria is respiring SO4, which I also do not believe can be sustained long term in a healthy tank.

Too add the organics that the dentirifing bacteria need, comes from the bacteria dying that need O2. So as the bigger fauna stir the bed and add O2, that bacteria blooms. As that area is left alone for a long enough period of time, the O2 will reduce, O2 respirinig bacteria die, and NO3 respiring bacteria bloom using the organics from the dead bacteria. Yes there is a small amount of NO3 release from the bacteria dying, but not enough to sustain them long term. that is where the water column NO3 starts getting used.

Maybe.

I understand the reactions taking place (I think) and cover them in my articles.

But I still see a logistics problem with requiring the faster diffusing O2 to be depleted (by a nitrate-producing process) while the slower diffusing nitrate needs to go deeper for denitrification instead of diffusing back out.

In any case, I cannot prove anything. It just seems complicated to me.

 

[brandon429]

I once wiped out half a setup on nano-reef.com putting opinions in on how to transfer tanks probably in '09. Luckily he forgave me wasn't mad. Severe clouding did it


It was terribly embarrassing, though, and a hyperfocus on preventing that from ever happening again resulted and we did reach that control level in my opinion



The reason none have died since then is attributed to sandbed rinsing, which is neutralization of the variables seen causing losses in pattern here:

https://www.reef2reef.com/threads/sand-bed.977451/
https://www.reef2reef.com/threads/cloudy-water-dead-fish.1060132/
I once had about twenty of those examples stored up for proofing but have since let the older ones go. We don't require proof anymore as word got around well enough that sometimes sandbeds can crash a reef.

A rinsed sandbed can never never crash a reef

There's a new skip cycle red sea tank transfer coming soon. Results brought by: sandbed rinsing

I know for others sandbeds don't harm reef tanks and those two examples above weren't sandbed caused.


But I guarantee, personally guarantee, if anyone reading agrees to consult someone's ten thousand dollar reef transfer and you kill it, rinsing is the first thing you'll resort to. It only seems crazy, but in the end that's what delivers the results


Not allowing waste, detritus, in states of decay to present in transferred tanks is the secret to perfect reef tank handling results.


That doesn't mean a reefing matter can't run a sandbed anyway they like and it wouldn't run

But for the public? You better be rinsing that stuff or the apologies will sting one day

If you rinse, advise rinsing, you get luv

 

[sgdnycct]

O2 respiration does not directly create NO3, as I am sure you know. The vast majority of NO3 come from fish waste as ammonia. The vast majority of organics on the bottom are carbohydrates from dying bacteria, which is CH2O , in some form or another. Very little NO3 is actually produced in the sand bed itself. I will look through my Chem ocean books on this matter to find a better graph and data on the matter, but all it takes is the right depth and O2 levels for denitrification to setup. that depth is dependent on organics in the sediment.

The amount of Denitrification that happens is also dependent as stated how much NO3 is reaching the hypoxic areas. I do not believe a DSB will continue to denitrify a tank with constant 0ppm NO3. The main NO3 reduction is done in algae and will be used there before reaching the sand bed. The production of H2S begins where dentirification ends, usually by that point the areas of H2S production is completely annoxic and the bacteria is respiring SO4, which I also do not believe can be sustained long term in a healthy tank.

Too add the organics that the dentirifing bacteria need, comes from the bacteria dying that need O2. So as the bigger fauna stir the bed and add O2, that bacteria blooms. As that area is left alone for a long enough period of time, the O2 will reduce, O2 respirinig bacteria die, and NO3 respiring bacteria bloom using the organics from the dead bacteria. Yes there is a small amount of NO3 release from the bacteria dying, but not enough to sustain them long term. that is where the water column NO3 starts getting used.

WOW! I am no chemist but I think I kinda sorta understood this. THANK YOU!!

Again, I'm no chemist or biologist. I'll explain how I picture it working in my head via en example. Ill use worms- probably thousand of varieties in the wild who knows how many in my tank. Worms live in the sand. They create tunnels and come up to the surface to suck in nutrients from the water column or surface (waste, chemicals, leftover food, etc.). They poop it out in the sand. Other worms in the sand eat that and convert it to something. Other living things eat that and goes down the chain until... bubbles out as gas? Take the worm and multiply it by 1000 or 1000000 or more 24x7 and bobs your uncle. They live and die. If the DSB is healthy and a has large variety of critters, as things die new things will grow and reproduce to absorb the waste.

BUT it has to be healthy and that requires a large variety of creatures living in the biome. Over time because it's a closed system something will out compete other things: a cycle that keeps repeating. Over time the DSB no longer has the variety needed to handle all the types of nutrients in the system and then... who knows- maybe it crashes the tank, maybe it just causes algae to grow like crazy and/or nutrients to collect in the water column, maybe it just looks ugly and starts getting dirty. Whatever happens at this point it will need maintenance, otherwise only part of the cycle happens and waste starts accumulating.

I think the key is the variety in the biome and critters mixing the top layer so it looks nice. 1-2 times a year seed it with sand or piece of good live rock buried in the sand part way to introduce variety.

Probably a huge oversimplification and maybe not correct, but I think it's a simple way of saying what you wrote? Am I even close?

I didn't want to opine on DSB crashes, but I feel like ANY tank can crash for ALL KINDS of reasons. The one consistent story I hear is tanks crashing and never figuring out what happened or people deducing what most likely happened- which is probably the best we can all do. All I can do is say I've always had great luck with DSBs. I design my system to be low maintenance and I focus on fish and keep them fat. So far so good!

 

[CoastalTownLayabout]

It’s unfortunate more new hobbyists don’t use DSBs. They are a lot easier to have early success with than BB / dry rock starts. Fresh live rock and you’re good to go. I don’t even think live sand is necessary, the DSB should look Ants Canada within a month anyway if the rock is good.

Old tank syndrome doesn’t seem like a barrier for a new hobbyist. After a few years they’re probably looking at upgrading anyway if they’ve had initial success.

 

[areefer01]

Old tank syndrome doesn’t seem like a barrier for a new hobbyist. After a few years they’re probably looking at upgrading anyway if they’ve had initial success.

What is the hobby life expectancy of a new hobbyist these days? On the surface it seems that we have a high rate of attrition.

 

[sgdnycct]

What is the hobby life expectancy of a new hobbyist these days? On the surface it seems that we have a high rate of attrition.

Hmmm... that's a good question. How would one figure that out? I imagine once someone ends participation in the hobby they will also end their participation the chats.

 

[CoastalTownLayabout]

What is the hobby life expectancy of a new hobbyist these days? On the surface it seems that we have a high rate of attrition.

Probably less than 18 months for someone battling dinoflagellates or some other cursed pox because they expected immediate success with dry rock and a bare bottomed setup.

 

[reneeL]

I have always been a fan of DSBs. They can be very effective in helping reduce nitrates in a tank with a heavy bioload. Those of us that love fish and like to feed them well appreciate this benefit. Other than having some nassarius snails and an Atlantic cucumber, a DSB requires no maintenance at all. There is no vacuuming necessary.
However, I know that not everyone agrees that these benefits are worth the risks. I am curious about your thoughts and if it's based on your own personal experiences or hearsay from other reef keepers.

I will start. I have had 4 tanks with DSBs and all 4 flourished. The longest one was in a 90g tank from 2001 until 2012 and when I downsized that tank the sand smelled like the ocean and not sulfurous at all. The tank I have now is coming on its 8th year with a DSB. DSBs were common when folks were setting their reefs up according to the Berlin method. With a DSB it is important to leave the sandbed undisturbed except the top 1" to encourage anaerobic bacteria to colonize the deeper, low or no oxygen areas of the sandbed. Secondly, one does not want to release hydrogen sulfide gases into the tank in significant amounts as this can be deadly. However, I do feel the actual incidents of that occurring are much lower than folks think. I worked at a lfs for 12 years where my boss set up many of the store's client's tanks with DSBs. I maintained those tanks for years and years and never experienced even 1 crash due to gas poisoning. One of those tanks, ( belonging to a close friend of mine) had a very heavy bioload and a sandbed that was over 23 years old before a different accident crashed it. I would be curious to hear firsthand accounts of folks whose tank crashed from DSB poisoning and what brought on the incident. I would also like to hear from folks like myself who have had DSBs and never experienced a hydrogen sulfide poisoning event so the reef community as a whole can more accurately assess the risk of employing a DSB.

I had a 100 gallon, 2011 to 2017 with the DSB and no problem, took it down because of hurricane Harvey caused it to die, no electric for over a week. Just got back to my hobby March 2024. My sandbed is deeper in areas because we have jawfish. I am aware of the possible poison but have been lucky enough not to deal with it. Tried the miracle mud years ago, I am not going to do that this time. I have 3 tanks. Two are 40 gallon and a 180 gallon. Perhaps, I just have always had a busy CUC group. Jawfish do like a lot of sand and rubble.

 

[kdx7214]

So I am missing something here…. What’s a plenum?

Frequently people use an under gravel filter as seen in freshwater tanks.

 

[Randy Holmes-Farley Verified Community Expert]

It’s unfortunate more new hobbyists don’t use DSBs. They are a lot easier to have early success with than BB / dry rock starts. Fresh live rock and you’re good to go. I don’t even think live sand is necessary, the DSB should look Ants Canada within a month anyway if the rock is good.

So it’s your opinion that elevated nitrate is a significant cause of folks leaving the hobby?

I don’t know if that’s true or not, but I’d definitely recommend growing macroalgae before trying a dsb if nutrient reduction is the goal. Macroalgae has several big benefits aside from nitrate reduction that a dsb does not:

1. Phosphate reduction
2. Oxygenation
3. pH boost

 

[CoastalTownLayabout]

So it’s your opinion that elevated nitrate is a significant cause of folks leaving the hobby?

No, my opinion is that DSBs with good quality live rock provide a more stable environment in the starting phase of a system. Nutrient reduction does not seem to be the key issue beginners using dry rock, bare bottom, bottled bacteria starts usually face. Their issues seem to be more related to managing a period of instability with nutrient levels.

Not sure whether a refugium would assist but I’d encourage any beginner to consider a macro display. I have a macro display nano going at the moment and enjoy it as much as any other system I’ve kept.

 

[Randy Holmes-Farley Verified Community Expert]

No, my opinion is that DSBs with good quality live rock provide a more stable environment in the starting phase of a system. Nutrient reduction does not seem to be the key issue beginners using dry rock, bare bottom, bottled bacteria starts usually face. Their issues seem to be more related to managing a period of instability with nutrient levels.

Not sure whether a refugium would assist but I’d encourage any beginner to consider a macro display. I have a macro display nano going at the moment and enjoy it as much as any other system I’ve kept.

What aspect of the water do you believe a dsb stabilizes?

 

[PPBlimpy]

Frequently people use an under gravel filter as seen in freshwater tanks.

got it, yea never used under gravel filtration.

 

[VintageReefer]

I would call it a failure due to lack of knowledge. A DSB is not a set it and forget it approach. There are some requirements for success.

I would agree, and it takes years to determine how to do something properly and to discover if things work out long term and I don’t think even back then we had all the answers. There was a lot of mixed opinions on periodic cleaning vs don’t ever touch it

This is also a time where zero nitrates was heavily being pushed

 

[VintageReefer]

What low maintenance method that doesn't add equipment or chemicals? A DSB doesn't even require anything the first year or two. Then vacuum 25% 1-2" deep. Im still convinced if you put in a proper clean up crew and good flow vacuuming might not be necessary.

I have been using a 3-4” sandbed on the 75g reef tank next to me and I have not vacuumed, stirred, or done any manual cleaning, ever, and it’s been in use for 11 years. I run a mp40 and mp10, and can crank them to 100% and not get sand storms.

I feel this is ideal amount to have maximum benefits, minimum risk and minimum maintenance