locoyo386
Member
Originally Posted by natclanwy
http:///forum/post/2913202
I agree cleve's problem was due to excess CO2 not nitrogen gas, dissolved nitrogen won't effect the PH of the water where CO2 will. In stabilized saltwater the percentages of Nitrogen, Oxygen and CO2 will be the the same as air, 78%, 20.9%, and 0.033% respectively. As far a solubility is concerned though like spanko said nitrogen is half as soluble as oxygen, but CO2 is 1000 times more soluble than nitrogen or oxygen. In other words you can't really build up a significant amount of nitrogen or oxygen in saltwater over what is naturally present or at least not enough to be dangerous especially nitrogen since it is an inert gas. CO2 on the other hand readily dissolves into saltwater displacing oxygen and nitrogen and since CO2 is a reactive gas it forms carbonic acid in your tank lowering the PH.
As far as gases release from stirring a DSB I believe it is Hydrogen sulfide gas that is released from the sand bed which is formed when the denitrifying bacteria run out of nitrate while there is still decomposing organic matter and then some bacteria can use sulfate to metabolize organic matter and H2S is the byproduct. H2S is extremely toxic to your livestock and can cause mass die off if large quantities are released into your aquarium at once.
To get back to Locos topic,
Rock that is more porous or less dense has much more surface area than a dense rock will, and the pores do not necessarily need to be large they could be microscopic in size so even a piece of live rock that doesn't appear to have holes is usually covered in thousands of microscopic pores that water can diffuse through. Its through diffusion (I do beleive this is the correct word used) (diffusion isn't exactly the right word but I can't remember what the correct term is) that water is able to move deep inside the rock to anoxic areas of the rock where denitrification can occur. It is a similar process in a DSB but denser sand will form more anoxic areas then less dense sand allowing the sand bed to be shallower. In other words hypothetically lets say it takes 12" of crushed coral to form anoxic areas for denitration to occur, it would take maybe 3-4" of sugar sand to achieve the same amount of anoxic areas.
The outer surfaces of the LR is where the Nitrifying bacteria will reside and porous rock makes the surface of the rock more ruff increasing the surface area for bacteria to populate. For a comparison 1 square inch of rock probably has 100x the surface area of 1 square inch of glass so the rock has the ability to support 100x more bacteria than the glass.
WOW! you guys went way beyond my knowledge here. I have read though, that to achieve denitrification with "live rock" is very complicated. First the rock really has to qualify as "live rock" (has to come directly from a reef and be full of diverse live organisms that are well established within the pores of the rock. Has to be extremely well taken care of while transporting it to our tanks.). If it does indeed qualify, it has to be free from any algea that may occupy the pores. Even when this is attainable, the living organmisms cannot reproduce (at least some or most, not sure which) in captivity. Thus, the denitrification might occur but only for a limited time (not sure how long).
http:///forum/post/2913202
I agree cleve's problem was due to excess CO2 not nitrogen gas, dissolved nitrogen won't effect the PH of the water where CO2 will. In stabilized saltwater the percentages of Nitrogen, Oxygen and CO2 will be the the same as air, 78%, 20.9%, and 0.033% respectively. As far a solubility is concerned though like spanko said nitrogen is half as soluble as oxygen, but CO2 is 1000 times more soluble than nitrogen or oxygen. In other words you can't really build up a significant amount of nitrogen or oxygen in saltwater over what is naturally present or at least not enough to be dangerous especially nitrogen since it is an inert gas. CO2 on the other hand readily dissolves into saltwater displacing oxygen and nitrogen and since CO2 is a reactive gas it forms carbonic acid in your tank lowering the PH.
As far as gases release from stirring a DSB I believe it is Hydrogen sulfide gas that is released from the sand bed which is formed when the denitrifying bacteria run out of nitrate while there is still decomposing organic matter and then some bacteria can use sulfate to metabolize organic matter and H2S is the byproduct. H2S is extremely toxic to your livestock and can cause mass die off if large quantities are released into your aquarium at once.
To get back to Locos topic,
Rock that is more porous or less dense has much more surface area than a dense rock will, and the pores do not necessarily need to be large they could be microscopic in size so even a piece of live rock that doesn't appear to have holes is usually covered in thousands of microscopic pores that water can diffuse through. Its through diffusion (I do beleive this is the correct word used) (diffusion isn't exactly the right word but I can't remember what the correct term is) that water is able to move deep inside the rock to anoxic areas of the rock where denitrification can occur. It is a similar process in a DSB but denser sand will form more anoxic areas then less dense sand allowing the sand bed to be shallower. In other words hypothetically lets say it takes 12" of crushed coral to form anoxic areas for denitration to occur, it would take maybe 3-4" of sugar sand to achieve the same amount of anoxic areas.
The outer surfaces of the LR is where the Nitrifying bacteria will reside and porous rock makes the surface of the rock more ruff increasing the surface area for bacteria to populate. For a comparison 1 square inch of rock probably has 100x the surface area of 1 square inch of glass so the rock has the ability to support 100x more bacteria than the glass.
WOW! you guys went way beyond my knowledge here. I have read though, that to achieve denitrification with "live rock" is very complicated. First the rock really has to qualify as "live rock" (has to come directly from a reef and be full of diverse live organisms that are well established within the pores of the rock. Has to be extremely well taken care of while transporting it to our tanks.). If it does indeed qualify, it has to be free from any algea that may occupy the pores. Even when this is attainable, the living organmisms cannot reproduce (at least some or most, not sure which) in captivity. Thus, the denitrification might occur but only for a limited time (not sure how long).
