To Clean or not to clean Deep Sand Bed

[Promethius]

For the last three year my tank has done well, until recently…. At present I am having a problem with nitrates well over the 50ppm mark. Previous to this, the tank ran around 20ppm. With water changes, with adjustment to the skimmer, and fish being put on a diet, I can’t seem to get the nitrates down. The tank is full of softies and a half a dozen fish (all accounted for). So the next thing could the fault be with the sand bed? (3 years in action come May) Do I need to clean it or replace part of it? Any ideas?

[NewFish3]

From what Iam told here. If you vac it, do it very lightly. You dont want to disturbe the sand bed. There are things in the sand bed that you dont want to let go into the water. I think that they did say Nitrates.....but not sure

[ultimatemusky]

Do you run a refugium with macro algae? Since I started one up I have not had an issue with nitrates at all. Before I did I was continually doing H2O changes to keep it in check.

[Aquarist007]

how are you doing water changes--RH-F has suggested that 30 percent water changes once a month are the most effective in reducing nitrates
http://reefkeeping.com/issues/2005-10/rhf/index.php

I think it is a combination of things that reduce nitrates---once a week basting the sand bed lightly with a turkeybaster
having at a flow rate in the tank of at least 20 times the vol of the tank in gph
matching the flow rate through the sump to the output of your skimmer pump
adding the refugium as suggested by ultimatemusky

that said--what is your substrated--if it is crushed coral then that could be the problem, if it is argonite--is it still granular and loose--if so then it is probably not the problem

[Aquarist007]

Originally posted by NewFish3
From what Iam told here. If you vac it, do it very lightly. You dont want to disturbe the sand bed. There are things in the sand bed that you dont want to let go into the water. I think that they did say Nitrates.....but not sure

the sand bed contains aerobic bacteria on and near the surface which reduce ammonia to nitrates. In sand beds between 3 and 6 inches anerobic bacteria are in the lower areas--these reduce nitrites to nitrates and eventually nitrogen which makes it to the surface in a perfect nitrogen cycle.
what happens is that the nitrogen gas can get trapped in there which isn't that bad but if you dose ect with epsome salts for magnesium you can get a build up of hydrogen sulfide gas in deeper sand beds--this gas is very harmfull to tank inhabitants if released.

[Tswifty]

Originally posted by capn_hylinur
the sand bed contains aerobic bacteria on and near the surface which reduce ammonia to nitrates. In sand beds between 3 and 6 inches anerobic bacteria are in the lower areas--these reduce nitrites to nitrates and eventually nitrogen which makes it to the surface in a perfect nitrogen cycle.
what happens is that the nitrogen gas can get trapped in there which isn't that bad but if you dose ect with epsome salts for magnesium you can get a build up of hydrogen sulfide gas in deeper sand beds--this gas is very harmfull to tank inhabitants if released.

This brings up a question that I have been meaning to ask... Because I am planing on incorporating a DSB in my tank... Is the hydrogen sufide gas "pockets" something that is inevitable over time, or can it be prevented by routing maintenance?

[Gary Majchrzak]

Originally posted by Promethius
For the last three year my tank has done well, until recently…. At present I am having a problem with nitrates well over the 50ppm mark. Previous to this, the tank ran around 20ppm. With water changes, with adjustment to the skimmer, and fish being put on a diet, I can’t seem to get the nitrates down. The tank is full of softies and a half a dozen fish (all accounted for). So the next thing could the fault be with the sand bed? (3 years in action come May) Do I need to clean it or replace part of it? Any ideas?

how do the softies and fishes look... are they doing well or is something not looking healthy or are you just concerned about numbers on your test kit? (A lot of fishes and soft corals will tolerate rather high nitrates.) Are you running any bioballs (wet/dry) for biological filtration?
The lit refugium to grow/harvest macroalgae is a good idea for reducing nitrates.
If you don't have any livestock in the display that relies on a DSB for survival (such as Wrasses that sleep in the sand) I'd remove it and set up a RDSB (remote deep sand bed).
Removing my (several year old) DSB was the ticket for reviving coral growth in my previous aquarium.

[tmz]

I agree with Gary,older sandbeds can become exhuasted nutrient sinks.Remote sandbeds make more sense if the purpose is denitrication..

In deep beds anoxic zones develop where there is little or no oxygen. It gets used up as the water travels slowly down to them. Bacteria then resort to using sulfide and hydrogen creating hydrogen sulfide gases which when released can be toxic. Since most sand beds are under rock I think continuos stirring would be impossible even with sand sifting critters .Deep stirring might also defeat the denitrification proces by bringing oxygen to the oxygen poor zones to the detriment of the bacteria that convert nitrate to free nitorgen.. So it is proably inevitable to have some buildup over time.

[Promethius]

Thanks for the replies guys
Over the last 3 weeks I’ve been replacing about 20% of the water to drive the nitrates down with little success. Fortunately the high nitrates have not affected the fish at all, though some of the corals are showing some dislike to the conditions. Unfortunately, the bird nose wrasse may not appreciate the complete removal of the DSB, so it would need to stay.
When I originally set up the tank I made platform for the live rock to sit on so water movement over the sand would not be restricted, and I would end up with dead zones.
I also run a refugium the only thing that seems to want to grow in there is cyno (nice thick red blankets of the stuff which has smothered everything.)
Perhaps it’s time to remove the sand and replace it, the tank needs a little maintenance on the back anyway.
Thanks Steve

[Promethius]

Sorry guys I ment 20% water change each week

[Aquarist007]

Originally posted by Tswifty8
This brings up a question that I have been meaning to ask... Because I am planing on incorporating a DSB in my tank... Is the hydrogen sufide gas "pockets" something that is inevitable over time, or can it be prevented by routing maintenance?

hydrogen sulfide is a problem when epsom salts are used to dose for magnesium

[Promethius]

I don't think I'll dose with magnesium, since I don't test for it anyway.
The bed it's self seems to be working as the image shows

It's like this all around the tank. Just won’t bring the nitrates down. I’ve just tested it and it's at 50ppm, so I’ll do another water change tomorrow.
If I change the bed it'll mean I will have to cycle the tank and I'm not sure how Snorky (the bird nose wrasse) will handle being in a smaller tank, (He splashes enough now) during those weeks.

[bertoni]

Epsom salts won't cause hydrogen sulfide buildup, and the issue is probably not that important in any case, since it'd take a major sand disturbance to release any dangerous amount of gas. I have had a sandbed running now for 6 years with no issues, and the hydrogen sulfide level seems very low, from my attempts at interstitial water testing. Some hydrogen sulfide is going to be present in the anoxic region, though.

The gas pockets might be nitrogen, or they might be oxygen, since the sand is exposed to light along the sides. Depending on how the sandbed was set up and stocked, it might be doing some denitrification, but a refugium can do a lot, too, and might be easier to maintain.

I've not been convinced that getting the solid nutrients from the tank to a remote DSB is very practical for a lot of people, but it might work.

[tmz]

Originally posted by bertoni
Epsom salts won't cause hydrogen sulfide buildup, and the issue is probably not that important in any case, since it'd take a major sand disturbance to release any dangerous amount of gas. I have had a sandbed running now for 6 years with no issues, and the hydrogen sulfide level seems very low, from my attempts at interstitial water testing. Some hydrogen sulfide is going to be present in the anoxic region, though.

The gas pockets might be nitrogen, or they might be oxygen, since the sand is exposed to light along the sides. Depending on how the sandbed was set up and stocked, it might be doing some denitrification, but a refugium can do a lot, too, and might be easier to maintain.

I've not been convinced that getting the solid nutrients from the tank to a remote DSB is very practical for a lot of people, but it might work.

I also have a dsb in one of my tanks(lps dominated). It has been running for over 5yrs. Do you believe sand becomes exhausted after this period of time and needs replacement?The tank looks fine but many caution me to change out the sand since it's too old. I don't really wan't to take the tank down but I'm becoming concerned about the age of the sand. Is the old sand issue a misconception?
It is a 90 g integrated into a 500g system( the system has undetectable nitrate and phosphate). I also run a refugium with chaetomorpha.

[bertoni]

I don't think there's any timer that expires and requires that the sand in a tank be changed. If the tank is maintained well and stocked properly, I think the sand can last a very long time, probably longer than most any tank is kept running.

[Promethius]

From what I can understand, is there may be no problem with the DSB and that the problem lies else were. The tank has been fine for the last 3 years something has gone wrong somewhere. On one of the mushroom corals the top has yellow patches on its top, and the polyps have not come out for the last 2 days, were the other leathers in the tank seem fine.
This may not be linked to the high nitrates. But another lurking problem.
If I was to introduce Epsom salts to the system what target amount would I be aiming for?

[sjm817]

I'm just about ready to set up my new 65G fuge to replace the old 30L one. Display is a 180, 75G sump and the fuge again, will be a 65G. The display has a SSB of 2 - 3". The fuge will have a DSB of ~ 8" and will also have Chaeto. The fuge is fed off a T from the return and drains back to the sump. The water has been filtered via filter socks and has been through the skimmer area before it hits the fuge, so the water is fairly "clean" before it gets there. I dont expect to have much detritus in the fuge.

How long will it take before the DSB becomes active and has the ability for denitirification?

[Aquarist007]

Originally posted by bertoni
Epsom salts won't cause hydrogen sulfide buildup, and the issue is probably not that important in any case, since it'd take a major sand disturbance to release any dangerous amount of gas. I have had a sandbed running now for 6 years with no issues, and the hydrogen sulfide level seems very low, from my attempts at interstitial water testing. Some hydrogen sulfide is going to be present in the anoxic region, though.

The gas pockets might be nitrogen, or they might be oxygen, since the sand is exposed to light along the sides. Depending on how the sandbed was set up and stocked, it might be doing some denitrification, but a refugium can do a lot, too, and might be easier to maintain.

I've not been convinced that getting the solid nutrients from the tank to a remote DSB is very practical for a lot of people, but it might work.

if epsom salts don't cause hydrogen sulfide---then I am confused here a bit----I have read in a number of posts that dosing for one of the water parameters can cause a build up of hydrogen sulfde in deep sand beds
which substance was that?

[Aquarist007]

Originally posted by tmz
I agree with Gary,older sandbeds can become exhuasted nutrient sinks.Remote sandbeds make more sense if the purpose is denitrication..

In deep beds anoxic zones develop where there is little or no oxygen. It gets used up as the water travels slowly down to them. Bacteria then resort to using sulfide and hydrogen creating hydrogen sulfide gases which when released can be toxic. Since most sand beds are under rock I think continuos stirring would be impossible even with sand sifting critters .Deep stirring might also defeat the denitrification proces by bringing oxygen to the oxygen poor zones to the detriment of the bacteria that convert nitrate to free nitorgen.. So it is proably inevitable to have some buildup over time.

awesome learning here --Gary and Tom--thanks

when you mention deep sand beds and this process---what depth sand beds are you referring to.

I have picked up the concept at RC that the ideal sandbed seems to be 3-5 inches where you get aerobic and anerobic bacteria plus good depth for critters that live in and on it. Plus you don't get the build up of gases as in deep sand beds?

[tmz]

I'm referring to 4 plus inches as dsb.

[tmz]

Originally posted by sjm817
I'm just about ready to set up my new 65G fuge to replace the old 30L one. Display is a 180, 75G sump and the fuge again, will be a 65G. The display has a SSB of 2 - 3". The fuge will have a DSB of ~ 8" and will also have Chaeto. The fuge is fed off a T from the return and drains back to the sump. The water has been filtered via filter socks and has been through the skimmer area before it hits the fuge, so the water is fairly "clean" before it gets there. I dont expect to have much detritus in the fuge.

How long will it take before the DSB becomes active and has the ability for denitirification?

Sounds like a good plan. Although in my experience sand beds under chaetomorpha or other maroalgaes tend to get very messy. As a personal preference I use bare bottom in the refugium with chaetomorpha and some red kelp.Don't know how long untill it's denitrifying on all cylinders.. Depends on the amount of nutrient, how you seed the bed and how effective your flow is at establishing advection( water passing over the top of the sand creates a variation in water pressure which causes the water to move downward) to feed the anoxic zones. An average of 2 months or so may not be far off.

[tmz]

Originally posted by bertoni
I don't think there's any timer that expires and requires that the sand in a tank be changed. If the tank is maintained well and stocked properly, I think the sand can last a very long time, probably longer than most any tank is kept running.

Thanks I think I'll hold off on changing the sand and continue to rely on observation( absence of nusiance organisms and coral health) as a timer.

[papagimp]

Originally posted by Tswifty8
This brings up a question that I have been meaning to ask... Because I am planing on incorporating a DSB in my tank... Is the hydrogen sufide gas "pockets" something that is inevitable over time, or can it be prevented by routing maintenance?

doubtful it'll even be an issue Tswifty. Most tanks nver incorporate a DSB sufficiently deep to even get these pockets, run a 8-12" sandbed and ya may have some small pockets that don't stick around for very long. Ron Shimek has some good information bout this subject. http://www.ronshimek.com/Online%20Articles%201.htm Not sure if theres anything listed here on it, but a good place to start anyways.

[papagimp]

BTW, if the nitrates WERE running about 20ppm and now around 50ppm, doesn't sound like you had a very effective DSB. ya realize it's more than just a pile of sand needed. May need to revamp any microinfauna populations in the sandbed. Like a refugium booster pack or something. Most tanks won't contain sufficeint amounts or able to develope self sustaining populations of many of the microlife needed to properly stire up a deep sand bed, without it being naturally stired up, not going to be as effective.

Just a few thoughts.

[bertoni]

I don't know of any additive to the tank that'll cause hydrogen sulfide buildup, except perhaps too much food. That and not enough animals in the sand might make a mess.

As far as adding epsom salt, I personally dose a mix of magnesium chloride and epsom salt, to keep the ionic balance closer to seawater. I target about 1300 ppm magnesium, and dose accordingly.

I agree that many, if not most, deep sand beds probably aren't functioning very well. I don't think getting the right sand and animal stocking is easy.