Denitrification v. Nitrification

[mistermikev]

I have heard/read somewhere that in rare cases fish might cure themselves of ich by purposely going into high current areas... I know, sounds silly: but it wouldn't surprise me if it were true. Needless to say a high flow rate will keep detrius suspended and allow for more rapid denitrification, as far as I know there aren't any ill effects from it... other than to mushrooms!;)

[mistermikev]

"By the same token, the sand bed doesn't negatively nor positively impact fish diseases except those few parasites that need a substrate as part of their life cycle. "
-aren't high nitrite and nitrate the cause of bacterial infection?

[leebca]

Often, fish will remain semi-stationary in a strong water stream in the aquarium because they are ill or in poor water quality, and the flowing water makes it easier for them to breath. Also, the flowing water has a 'scratching' effect to a mild itch. The fish doesn't effect any cure to its health by doing this, other than to divert some energy to its immune system. Unfortunately, it's not enough energy to effect a cure.

What fishes can do with regards to Marine Ich (Cryptocaryon irritans) is develop and immunity. Not all do before they succumb to the parasite; not all can because of their physiology; and some find it a challenge because of the make up of their mucous coating.

What you've heard is untrue to the best of my knowledge.

Nitrite and nitrate concentrations are produced by the bacteria aquarists want to have in their aquarium. These bacteria do not infect fish. There are so many bacteria in the water (not connected with the nitrite and nitrate production) that they attack the weak, injured, ill, or undernourished fish much quicker than the good bacteria would care to.

Denitrification is the converting of nitrates to nitrogen and ammonia. This is not done while the detritus is in suspension because the bacterial organisms that do this don't like oxygenated water. They prefer the low oxygen content water like in the lower regions of a deep sand bed. Denitrification also occurs by having live rock. This takes place inside the rock, not on its surface, because the bacteria that do this don't live in oxygenated waters.

Nitrification is the converting of ammonia to nitrites and then to nitrates. this is also referred to as the nitrogen cycle and is a large portion (if not all) of what is referred to as the biological filter. Circulation brings these 'nutrients' ('nutrients' to the bacteria; wastes in the water) to their appropriate bacteria. Suspended detritus adds to the nitrates and thus is best removed when it is found (or not allowed to accumulate by regular maintenance of sand bed, filters, sump, and other places it accumulates.)

You may wish to get a marine aquarium book to go through the terminology and chemistry. Since you have familiarity with the hobby I think you'd find The Conscientious Marine Aquarist useful.

[mistermikev]

"This is not done while the detritus is in suspension because the bacterial organisms that do this don't like oxygenated water" I simply meant that when detrius is in suspension it is picked up by the filter more aptly... this in turn would lead to a denitrifying effect as the detrius is collected by the filter, followed by you changing your filter.

[mistermikev]

PS... my intelligence is kind of offended. I almost feel I need to defend it. Don't take me too seriously but denitrification does have a general definition that does not specifically refer to the cycle you mentioned.

remove nitrogen from; "Denitrify the soil"
wordnet.princeton.edu/perl/webw

[leebca]

I began a new thread for this discussion to keep thread topic integrity.

Sorry mistermikev. No offense meant, but I need to make sure the other readers understand the meaning of denitrification and nitrification. Your posts are mixing the terms.

As I mentioned earlier, denitrification is performed by microorganisms in a low oxygen content area. This low oxygen condition doesn't occur in a mechanical filter. The mechanical filter traps detritus (organic 'dirt') that is suspended in the water, but the detritus trapped in the mechanical filter is nitrifying (not denitrifying). The water passing through the mechanical filter contains oxygen which would suspend the life functions of denitrification bacteria. But with that available oxygen, the nitrifying bacteria take over in the mechanical filter.

Detritus decays into ammonia and other products. The ammonia goes to bacteria that makes nitrites. That leads to nitrate. This chemical process is called nitrification. Nitrogen is not being removed in this process, it is being chemically changed. This is what happens in a mechanical filter with trapped detritus -- additional nitrification. That is why I mentioned that detritus leads to additional nitrates in the marine tank water.

The denitrification and nitrification processes are all part of the nitrogen cycle. But each goes in the 'opposite direction,' chemically.

When that nitrate is converted to nitrogen gas (through nitrite) that is called denitrification. This requires bacteria that carry out their life functions without oxygen (anaerobic bacteria) or in low oxygen (anoxic) areas which are not generally found in a mechanical filter. Water passing through a mechanical filter carries oxygen with it and promotes nitrification.

When the nitrogen escapes the water as a gas, that is the loss of nitrogen that is connected with the simplified interpretation of the word 'denitrification.' The nitrogen gas is the result of anaerobic bacteria in the denitrifying processes, located in anoxic places (deep sand bed, for instance).

You are correct in that this chemical process (denitrification) occurs in the soil -- in the areas of soil where there is little or no oxygen. (Environmentalists refer to such areas as hypoxic, I think). It also occurs in marine tank deep sand beds (in the lower/deeper regions where there is little oxygen, called anoxic areas, when connected to the sea).

For additional information, check out: Denitrification - Wikipedia, the free encyclopedia

[CSeaSee]

-aren't high nitrite and nitrate the cause of bacterial infection?

I think leebca addressed this, but I wanted to state it again. High nitrite and nitrate don't cause a bacterial infection. High nitrite will kill a fish outright, because fish physiology, life, and high (or even low) nitrite levels are not compatible (in rather simple terms). High nitrate levels can stress a fish and lower its immune response. An immune system weakened by ANY means can lead to opportunistic infections by any pathogen... or not.

[leebca]

You bring up a point that had gotten by me, Carl. Perhaps mistermikev was confusing nitrite poisioning with a bacterial infection.

Regarding nitrates and marine fishes, remember that nitrate levels that cause some concerns to fishes are in the multiple hundreds of ppm.