Lowering Nitrates.
- Thread starter Neoz
- Start date
Gary Majchrzak
Team RC
if I'm correct this type of LR is full of large holes and has little interior mass. Not the best for denitrification.
Think solid and porous. (I realize it sounds like an oxymoron.) Denitrification happens in the interior of the rock. You need significant interior mass.
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Gary Majchrzak
Team RC
IMO/IME (and that of several notable others) this isn't true.
Coralline growth does not block or hinder the denitrification process that happens inside liverock.
The accumulation of PO4 (inside rock and/or DSB) over time can lead to what's commonly called "old tank syndrome".
Live rock can reduce nitrates quite well. Any surface material can host bacteria including sand . I've kept deep sand beds and tanks without them do just as well in terms of nitrates. Obviously the sand adds more surface area and the deeper it is the more surface you have but without food including organic carbon, nitrogen and phosphate no denitrifying bacteria will grow since they are heterotrophic which means they do not produce the organic carbon they need as their autotrophic cousins do. I've read the study several times ;it's detailed and accurate in my opinion. I would only add that deeper beds can be effective with sand critters to provide channeling and/ or some advective flow to move the nutrients to the bacteria.
That stinky smell Mel noted inside a broken rock is likely hydrogen sulfide formed deep in the rock where anoxic areas(no oxygen and no nitrate bearing oxygen) form particularly rock that has been sitting around without much water movement.
The heterotrophic bacteria involved in the nitrification and denitrification are faculative. That means they can use free oxygen for energy or pull it from NO3(nitrate) or even SO4(sulfate).
They are also benthic( they live on surfaces) as opposed to planktonic(living in the comparatively oxygen rich water column).
They will use what's most rewarding for them first and that's oxygen, functioning aerobically .
It takes more work to pull it from the NO3 via anaerobic activity ;so why bother except when the area they are in runs low in oxygen (hypoxic). So when all of the oxygen is used up they turn to the oxygen in the NO3 which is less rewarding but still of use to them.. The cited study shows hypoxic areas and anaerobic activity happens at very shallow depths. It can even happen within the bacterial colony itself.
When they exhaust all of the NO3, the water becomes anoxic,they turn to the even more difficult task of pulling oxygen from SO4(sulfate) which is present in vast quantities in salt water(2700ppm). In the process of reducing SO4 , hydrogen sulfide(sewer gas) a toxin is produced as a by product. It will likely breakdown before any escapes from the rock but may be easily released in a deep sand bed.
To perform any of these oxygen reductions they need organic carbon, nitrogen and phosphorous to proliferate.They use the oxygen they gather for energy just like we do via respiration.
Generating enough water movement to to carry organic carbon, nitrogen and phosphorous while still allowing low oxygen areas to form without anoxia is what sets the stage for denitrification.
The heterotrophic bacteria involved in the nitrification and denitrification are faculative. That means they can use free oxygen for energy or pull it from NO3(nitrate) or even SO4(sulfate).
They are also benthic( they live on surfaces) as opposed to planktonic(living in the comparatively oxygen rich water column).
They will use what's most rewarding for them first and that's oxygen, functioning aerobically .
It takes more work to pull it from the NO3 via anaerobic activity ;so why bother except when the area they are in runs low in oxygen (hypoxic). So when all of the oxygen is used up they turn to the oxygen in the NO3 which is less rewarding but still of use to them.. The cited study shows hypoxic areas and anaerobic activity happens at very shallow depths. It can even happen within the bacterial colony itself.
When they exhaust all of the NO3, the water becomes anoxic,they turn to the even more difficult task of pulling oxygen from SO4(sulfate) which is present in vast quantities in salt water(2700ppm). In the process of reducing SO4 , hydrogen sulfide(sewer gas) a toxin is produced as a by product. It will likely breakdown before any escapes from the rock but may be easily released in a deep sand bed.
To perform any of these oxygen reductions they need organic carbon, nitrogen and phosphorous to proliferate.They use the oxygen they gather for energy just like we do via respiration.
Generating enough water movement to to carry organic carbon, nitrogen and phosphorous while still allowing low oxygen areas to form without anoxia is what sets the stage for denitrification.
Steve Canyon
New member
I'm with Kat. I love reading these posts! One day, I hope to have learned enough to contribute something worthwhile.
Tom, Thank you. You really lend a credibility to the thread. (as well as every other one you post in.)
The links, the studies, and the explanation of the studies make learning easy for those of us that want to.
Tom, Thank you. You really lend a credibility to the thread. (as well as every other one you post in.)
The links, the studies, and the explanation of the studies make learning easy for those of us that want to.
dreaminmel
New member
Perhaps I should have used the word can vs. will, but I've had pieces of live rock get completely coated in coralline in the past. As in there were only two or three little holes left in the rock. Would it not be correct to assume that if the water is less able to enter the rock, the bacteria are less able to process it?
Not debating the other possible causes of old tank syndrome, PO4 buildup can definately be another culprit.
johno4
New member
Thanks for the rundown Tom.
Mel your idea does make some sense, however the rock I used wasnt covered with coralline so I would rule that out. Although I do think that could be an issue for some peoples tanks.
Graves, from my understanding the process of Assimilation is where the nitrates are used up by plants. Thats why a refugium full of macro helps out with lowering nitrates.
Gary, I still think that liverock should have lowered nitrates in my bucket. It just doesnt make sense.
Mel your idea does make some sense, however the rock I used wasnt covered with coralline so I would rule that out. Although I do think that could be an issue for some peoples tanks.
Graves, from my understanding the process of Assimilation is where the nitrates are used up by plants. Thats why a refugium full of macro helps out with lowering nitrates.
Gary, I still think that liverock should have lowered nitrates in my bucket. It just doesnt make sense.
-John,
Hmmmmmm,maybe its a little vague and being missed.Let me get right back to you on this a little tied up at the moment.In short the pic does show possibly why you have not seen any drop in Nitrate.
johno4
New member
While were on the topic of nitrate reduction can someone explain to me why a porous rock can house dinitrifying bacteria but other porous filter media cannont. This always confusses me as well.
PS. Neoz I hope you dont think I have hijacked your thead, I am just trying to add to the discussion.
PS. Neoz I hope you dont think I have hijacked your thead, I am just trying to add to the discussion.
You are welcome John and Steve.
Coraline vs denitrification and "old tank syndrome".
Surface area, CNP( carbon, nitrogen. phosphorous) and hypoxic areas are needed for denitrification..
While porosity is important, in my opinion coraline algae will not have any negative effect on denitrification and will likely help to limit nitrate since coraline needs nitrogen too.
If it clogs some areas of rock surface, water will move in in other places and likely permeates the coraline itself. Sometimes bacterial mulm itself may clog pores, wether in sand or rock.
Most nutrient processing occurs as water moves up trough the rock as a consequence of the advective current produced by water hitting the rock structure. I think in a typical reef tank there would always be plenty of shady non coraline areas on the rock in any case.
If a tank becomes more prone to difficulty(hair lagae , high nutrients) with age, I would suspect an acummulation of phosphate(PO4), metals,organics, etc on the rock ,rather than a nitrate issue. Nitrate is more transient.
Coraline vs denitrification and "old tank syndrome".
Surface area, CNP( carbon, nitrogen. phosphorous) and hypoxic areas are needed for denitrification..
While porosity is important, in my opinion coraline algae will not have any negative effect on denitrification and will likely help to limit nitrate since coraline needs nitrogen too.
If it clogs some areas of rock surface, water will move in in other places and likely permeates the coraline itself. Sometimes bacterial mulm itself may clog pores, wether in sand or rock.
Most nutrient processing occurs as water moves up trough the rock as a consequence of the advective current produced by water hitting the rock structure. I think in a typical reef tank there would always be plenty of shady non coraline areas on the rock in any case.
If a tank becomes more prone to difficulty(hair lagae , high nutrients) with age, I would suspect an acummulation of phosphate(PO4), metals,organics, etc on the rock ,rather than a nitrate issue. Nitrate is more transient.
Porous media other than live rock will indeed house denitrifying bacteria. Used granulated activated carbon. Sea chem matrix media, sulfur beads, etc are some examples.
A bucket of rock with no nitrate reduction could be for a number reasons. Testing error, zero PO4 or organic carbon , sterile rock,temperature , time and flow in the buckett are just a few of the variables. I have always tested 0 nitrate in the water from rock curing containers after curing it for a month or two
A bucket of rock with no nitrate reduction could be for a number reasons. Testing error, zero PO4 or organic carbon , sterile rock,temperature , time and flow in the buckett are just a few of the variables. I have always tested 0 nitrate in the water from rock curing containers after curing it for a month or two
- just to clarify this a bit,
Ok, will start with adding fishfood,note the center of the pic decomposers as we know if its not boundup in growth,removed by filtrations or water changes its safe to say its decomposing.This starts the process of ammoniafication the byproduct of that moves to the next nitrifying bacteria convert ammonia ammonium NH3/4 to no2 nitrte again byproduct N03 Nitrate.Im trying to keep this short but realize plants could assimilate N03 or more likely ammonium.Still nitrogen cycling we know takes place.
So this is where the pathway can be skewed.Aquarium literature for the most part tells us denitrfying bacteria convert Nitrate (N03) to harmless nitrogen gas(note top of pic) and that it would escape to the atomoshere,that is true but other bacteria such as cyanobacterium is one I know can fixiate Nitrogen and the byproduct is once again ammonia/ ammonium.(note top of pic traveling down the left side of pic)
I dont know if its why you haven't seen a drop in N03 with the liverock in the bucket but it is possible.
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Gary Majchrzak
Team RC
other porous filter media such as what?
I don't recall any porous filter media that resembles live rock... except perhaps manmade (artificial) liverock. Nothing performs denitrification like liverock except (in certain cases) a deep sand bed.
Take a nice solid chunk of liverock and crack it open with a hammer. The pores inside the rock (actually dead coral skeleton) is where denitrification takes place. Corallines don't inhibit the process at all IME.
Gary Majchrzak
Team RC
stirring up a deep sand bed (DSB) is a big no no.
Slurping up sandbed with a siphon doesn't release bad things (if done properly).
