Natural Nitrate Reduction

[Tanzy]

Phang,

I thought I'll start a new thread and answer your question here.

NNR or Natural Nitrate Reduction is acheived using bacteria and other microfauna present in the system, normally in the DSB or LR without using denitrators or nitrate absorbing/adsorbing chemicals. The word is 'Natural'.

This is acheived mainly by anaerobic bacteria which uses NO3 or nitrate as a electron acceptor instead of oxygen as aerobic organisms(You, me and some people reading this) would. Simply put, these bacteria 'breathe' nitrate ions instead of oxygen gas. The result of the nitrate metabolism is N2 or nitrogen gas. The hope is that nitrates will be converted into gas which will escape the system and in turn result in a form of nitrogen export for the system.

To allow anaerobic denitrification to take place, you must provide an anaerobic or anoxic areas in the system. In the case of most reef aquarium it would be in the core of the liverock or in a deep sand bed. The deep sand being there to allow an oxygen gradient to develope with higher concentration on the top and low or zero oxygen at the bottom. There should be minimal physical water movement in the sand, mostly it works by diffusion.

There is a nearly inexhautible amount of info on NNR available on the web. Go take a look! What I present here is a brief and simplified concept.

http://www.reefs.org/library/talklog/r_shi...mek_090698.html

http://www.reefkeepers.org/faq/cache/33.html

http://www.reefs.org/library/talklog/p_aug...ger_081599.html

I've got a few URL above that might interest you. Don't forget you must be able to export Phosphates too!

[Phang]

Hi Tanzy,

Thanks for the information,

There is an issue here also that you might have to help me link up...

It is highly encouraged to have organisms to shift the sand so as to prevent dead areas in the DSB...

However from my understanding, the deep areas whether anaerobic (or low/zero oxygen levels) are, wouldn't sand shifting and movement or movement of sand prevent this from happening???

Again the phleum system should also work on this function, or else why did theory suggest the usage of nettings in the lower level to prevent critters/sand sifters from disturbing the deeper areas of the sand bed .....

So, are we suppose to leave the DSB alone to encourage the development of this anaerobic areas ??????? or are we to encourage sand sifting...

Confused!!!!!!!!

[Phang]

OOps...

My question anwered through the URLs....heeheehee...

Now where or how could I get my DSB innoculate in the shortest period with these critters.....Live sand??? where do you get this in the first place???

Anyone out there with a establish SB who can hand some to seed my tank????

And Sifting stars, Sleeper gobies wouldn't be suitable as they consume these organisms so what else is appropriate besides sea cukes and urchins????

Sorry for the influx of questions....

[Achilles Tang]

Only the top layers of sandbed, DSB or Plenum, should be 'shifted' with sand-shifters. Once your sandbed is established, you will see worms, pods, even tiny brittlestars in your SB doing their stuff.

You are not to disturb the bottommost layer. Therefore, gobies, jawfishes & sand-burrowing seastars are a no-no. If they are DSB creature-eating, a BIG NO NO!

If you want to innoculate your new DSB, transfer a small amount of old sand from an established tank and it should work.

Perhaps next time, we can do a cup-o-sand exchange program whenever the SRC members meet!

Hope this clears your mind!

[Phang]

would a netting between the 2 layers work???

maybe netting with holes only large enough for those critters...

or maybe acrylic sheets with lots of holes...

or even light diffusers....

SO... I refrain from sand sifting gobies, seastars....what else can I buy that would help sand sifting w/o hurting the population of critters......

[hongqixian]

Good idea, but we would need to develop some kind of quality control though.... or else might spread pests like flatworms...

Anoxic (low concentration of oxygen) is more efficient for removing nitrates than anaerobic (no oxygen). (I learnt this from saltaquarium.about.com but forgot the explanation already) So deeper doesn't mean better.

[Achilles Tang]

According to Dr Ron Shimek, he says that a functioning DSB should be min 6 inches. He recommends 8 to 12 inch (anything beyond that has diminishing returns but it's ridiculous in a reef tank unless you can dedicate a sump to have that much of height).

So the minimum height for a true and optimally functioning DSB should be 6 inches min.

Some aquarists have reported success with around 4 to 5 inches... but if i am not wrong, it's all oolithic sand (which we can't get from LFS locally and it also causes a sandstorm if you have strong circulation because it's so fine.... makes it harder to siphon detritus too as it will all come up together!).

[Tanzy]

Dead sand will become Live sand on it's own if left for a suitable period of time to mature. This is usually about less than one month for nitrification to start and about 3 months to a year for proper denitrification to set in. There is no need to add bacteria as all the bacterium you need is freely available from the air and in the LR. Adding sand from another established aquarium doesn't speed up the bacteria colonizing process but it does enrich the microfauna in your more or less sterile new setup.

Which brings us to the next point of microfauna. Sand stirrers stir the sand for a reason and that is to eat! They eat bristle worms, amphipods ...etc that are crucial for moving nutrients through the top layers of sand and consuming detritus. People buy these stuff in Detritivore packs while sleeper gobies & some starfish will happily mop them up for you. These microfauna are extremely crucial to a DSB, more so than a plenum system, because of the fine grains to prevent compaction and clumping of the sandbed for proper denitrification to take place. Sand bed fauna will also consume muck that lands on the sand and prevent detritus buildup, thereby removing the need for vacuuming the sand. In fact, many reefers feed the sand bed intentionally to increase the sand bed population. These microfauna are part of the denitrification by bringing nutrients into the anoxic regions of the sand to be utilised by the bacteria that use nitrates instead of oxygen to burn these nutrients. The above mentioned worms and pods are sand sifters in their own right.

Anaerobic regions produce Hydrogen sulphide or H2S that smells like rotten eggs. It is poisonous to most animals in a reef tank so naturally the existence of H2S is undesirable and many will strive to prevent the formation of H2S for that reason. Although it is poisonous, small amounts of H2S released by DSB is deemed to be quite harmless in a large enough system, but I stress small amounts. So there is always a danger when a DSB is disturbed to release large amounts of H2S.

I personally use a green netting to separate the sand into two parts. I suppose a light diffuser will work too. It's all to prevent larger animals, sometimes your grubby hands, from going too deep into the sand bed, worms and pods can easily get through even the netting.

[Achilles Tang]

Good contribution Tanzy! I have fibreglass mat screening standing by for my new DSB.

Phang, if you intend to get do a dsb or plenum and wish to protect the bottom most layer, you can use a netting of some kind like Tanzy said.

[mushroom]

Saw some CaribSea sugar-sized sand at Sealife last weekend.

Tempted to change my crushed-coral bed to a DSB in tank. Should I lay the oolithic sand over the old bed for a deeper sand bed (would it still act as a DSB if so) or must I remove the crushed-coral? A lot of effort to remove the entire existing bed, and somemore the CaribSea sand very expensive!

[Tanzy]

mushroom,

The biggest problem you will face is actually the dust in the fine sand that will make your water cloudy for days and eventually settling on your rocks too. I believe that adding the sand over the crush coral shouldn't be a problem if you don't have a thick layer of CC. How deep is it?

I'll recommend layering fine sand onto the existing crush coral at one inch a month until 4-6 inches is reached.

If you intend to remove the CC, then the best way to preserve the microfauna is to take out a quarter to about half the existing CC to the glass bottom then fill up the whole with new sand. Repeat with the other portion of CC 3 months later.

What's your filtering mechanism in the tank? If you use bioballs then it's relatively safe to move the CC but if the CC is part of your filtration then it pays to be careful and not rush things.

[Phang]

Hi Tanzy,

Thanks for all the infor...

Great help in clarifying doubts..

BTW, when will you be back in Singapore..??

Achilles,

I'm basically going for the DSB... now looking for the netting... was thinking of wrapping this green netting onto light diffusers ( the gaps too large) before separating the DSB...

Where did you buy the firbreglass nets and at what price??

anyone knows where I can get these large green nettings???

Mushroom,

How much is this Caribsea Sand???

And yes... before I forget,

I'm thinking of keeping Mandarins and a symbiotic team of Pistol and sleeper goby but heard that these fishes are a thread to this fauna in the sandbed.... any advise???

[Achilles Tang]

Go to any hardware store... they have rolls of it with different colour and netting hole sizes.

[Tanzy]

Phang,

I'll be back mid December.

Sleeper gobies(Valenciennea spp.) don't really live with with pistol shrimps(Family Alpheidae). A mated pair will dig their own burrow. I use to have a pair and the burrows are very deep. They like to dig under rocks so if you intend to have a DSB with sleepers then it is best that you have a 10 inch sand bed with netting 4 inch from the surface and PVC support under the LR to prevent a rock slide. I got rid of them because they were causing havoc with all the renovation work they were doing. Not forgetting that they eat all your beneficial sand bed creatures!

Only gobies in the genera Amblyeleotris, Cryptocentrus, Ctenogobiops, Istigobius, Stonogobiops will live together with pistol shrimps. They are also quite specific with what species of shrimps they live with. The most common gobies you can try are the Yellow Prawn Goby(Cryptocentrus cinctus) and Yellow-nose Prawn Goby(Stonogobiops xanthorhinica).

If you are using the netting, I don't see a reason why the light diffuser is required unless you intend to build a plenum. Make you life easier by plonking in half the sand, fill with water until the surface of the sand, stir it around a bit to release air bubbles, place the netting on top and add the rest of the sand.

[mushroom]

Phang,

Sealife quoted me $90 for 30lbs 0.5-1mm sized sand. They have various other sizes too. Probably can bargain it down.

Don't think the mandarin is a good idea unless you can produce live foods for it. I once bought a scooter blenny on impulse. It ate most of my microfauna before it starved to death.

Tanzy,

My current CC (of 2 - 5mm size) only 1.5 inches. I'm thinking that's why my nitrates are always around 10-15ppm (ammonia and nitrite is 0). I have bioballs and big coral chips in an internal overflow chamber. Also thinking of gradually removing the coral chips (trap detritus only as Achilles said), and the bioballs (most US websites say they are nitrate traps).

Any advise anyone? Thanks in advance.

[hongqixian]

Saw some CaribSea sugar-sized sand at Sealife last weekend.

Tempted to change my crushed-coral bed to a DSB in tank. Should I lay the oolithic sand over the old bed for a deeper sand bed (would it still act as a DSB if so) or must I remove the crushed-coral? A lot of effort to remove the entire existing bed, and somemore the CaribSea sand very expensive!

The cc would eventually move above the sugar sand.

[Phang]

Only gobies in the genera Amblyeleotris, Cryptocentrus, Ctenogobiops, Istigobius, Stonogobiops will live together with pistol shrimps. They are also quite specific with what species of shrimps they live with. The most common gobies you can try are the Yellow Prawn Goby(Cryptocentrus cinctus) and Yellow-nose Prawn Goby(Stonogobiops xanthorhinica).

Any pics to identify this creatures... make it easier to find them when scouting around...

Thanks

[Phang]

Sleeper gobies(Valenciennea spp.) don't really live with with pistol shrimps(Family Alpheidae). A mated pair will dig their own burrow. I use to have a pair and the burrows are very deep. They like to dig under rocks so if you intend to have a DSB with sleepers then it is best that you have a 10 inch sand bed with netting 4 inch from the surface and PVC support under the LR to prevent a rock slide. I got rid of them because they were causing havoc with all the renovation work they were doing. Not forgetting that they eat all your beneficial sand bed creatures!

If you are using the netting, I don't see a reason why the light diffuser is required unless you intend to build a plenum. Make you life easier by plonking in half the sand, fill with water until the surface of the sand, stir it around a bit to release air bubbles, place the netting on top and add the rest of the sand.

Maybe i could start up a mini tank with linkage to my sump....for these gobies...

Tanzy, the eggcrates are actually to support my LR... they will indirectly be supported by 2 inches glass (siliconed to bottom of tank) beneath them...

[Tanzy]

Cryptocentrus cinctus

Stonogobiops xanthorhinica

You should be able to find these gobies readily available at most fish shops.