Nitrate - question on LR & Filters???

[Tony B]

Can some one please explain why, when external biological filters (trickle filters, canister filters etc) are used in conjunction with lots of live rock it is commonly believed that you will end up with high nitrates?

How does the colonisation of aerobic bacteria within the external filters hamper the anaerobic bacteria (denitrification) of the LR?

It does not make sense to me?

[kim]

One idea is that the nitrates are introduced into your water via the trickle (or whatever), so are diluted and spread everywhere. The advantage of LR is that the nitrifying/denitrifying bacteria are very close to each other, so the latter are fed concentrated nitrate and deal with it before it escapes.

[wayne in norway]

You might also want to argue that if you believe your anaerobic bacteria sit in bacterial film on the live rock with a thin film of aerobic bacteria on top (likely situation, hard to imagine anything else), the aerobic film will actively prevent the anaerobic layer ever being exposed to the water dissolved nitrate.

[Glenn@home]

Its also worth thinking about where the baceria reside. Many think that the live rock is porous and the anerobic bacteira lives inside.

Im not doubting this is possible to an extent, but I would question the depth to which this takes place? My personal view is that most of the bacatiera we desire live close to the surface.

I would agree with Wayne in that its more likely that the ideal and typical case is where the aerobic and anerobic bacteria live very close together so that the conversion of nitrates folowed by denitrification takes place in a relativley confined area.

It would also explain quite nicely why the good circulation over and through live rock is critical to its efficient use to break down waste products efficiently as opposed to the flow of water through the live rock and the very small pores.

Clealry if you have a cannnister filter some of the waste is converted to nitrite and nitrates in an envirionment not rich in denitrifying bacteria

FWIW i dont buy the nitrate factory argument against the use of cannister filters.

IMHO filtration is about balance, whatever method of denitrification you use if the waste load exceeds the capability of the system to remove the waste then the system is out of balance.

SO going to basics if you feed to much and use water changes to remove nitrates you may not be able to remove sufficent nitrates to dilute it to an accpetable level easily.

It doesnt make water changes useless as a means of control only that the load and means for dealing with it need to be in balance.

JMHO

Glenn

[Horatii]

I use bioballs and I dont buy into the 'Nitrate Factory' rubbish cus people who spout it off can't give a proper explination for the reason. It just seems like a lemming response when people say they have a problem with nitrates and they use bioballs. Yet people who run a pure berlin method can and sometimes do end up with nitrates just as bad.
Neither do I believe that the nitrifying/denitrifying bacteria are very close together and work like some kind of chain gang. If so you could say that using ozone causes nitrate levels to rise as it breaks ammonia down straight to nitrate and away from the LR in the same manner as bioballs.

[kim]

I don't buy into the standard bioballs angle (totally)...I share your sceptism.

But I do buy into the "bacterial films".

Ozone converts ammonium into nitrate - true. But how much ammonium do you run, generally, without the ozoniser ? If near to zero, running ozone is not likely to be an obvious source of nitrates.

If not near zero, oops !

:)

kim

[wayne in norway]

While I do see a role for bioballs, and continue to use some filter material in my system that is certainly acting similarly I don't have too many doubts about the 'nitrate factory' story.
Lets look at the very basic point here. Ammonia to nitrate is an oxidative reaction. Nitrate to nitrogen is reductive. These reactions are 'encouraged' by enzymes produced and used by bacteria. Now unless your tank is very different to any I've ever seen (imagine a deep water, stagnant tank with a gentle rain of mud into it...) your tank is designed to be an oxidative enviroment. The enzymes produced by bacteria are not very strong. If you put an 'anaerobic bacteria' into your tank water, and expect it to reduce nitrate you will be disappointed - it cannot perform a reductive reaction in oxygen rich water. The bacteria will be there (and they are), but they will not be reducing any nitrate till you produce an area in the tank that is reduced in oxygen content to very low levels (but not zero).
So your efforts to get rid of nitrate are really going to be concentrated on creating areas of low oxygen content. I don't buy into the story that live rock is full of anaerobic bacteria doing this for you. I don't believe the pores in limestone are that well connected, rather the gaps between them are choked with other materials (another story), mostly clay minerals. I believe that the bacteria are concentrated on the surface of the LR, and that that surface includes porespaces connected to the external surface directly (this can extend some way into the mass of the rock tho). And yes Horatii I believe, from a basic knowledge of bacterial films, that you can, and do, have a layer a few microns thick of anaerobic bacteria overlain by another layer , some microns thick, of aerobic bacteria. So also I don't believe that there is a direct contact between these anaerobic bacteria and the tank water , so the removal of nitrate in tank water is not going to be done well, efficiently by utilising these bacteria alone.
If you want to get rid of water dissolved nitrate use something that promotes direct uptake of this nitrate - algae, phtosynthetic orgs (corals, clams....) or pump the water to a nitrate reactor or use advection to push it down into a sand bed.

Some points, notes...
Berlin systems traditionally do suffer creeping (or not so creeping) nitrate. My own opinion is that live rock is not an especially good medium for reduction of nitrate. The surface area available for reduction is not enough, and the whole berlin enviroment of live rock and either no substrate or a coarse substrate is too tuned to aerobic oxidative processes. So if the bioload is too high, and the mass of rock or too low, you get a problem. This was solved in a few ways by either adding a nitrate reducing device (European solution?) or by using algae or a dsb (US solutions? Maybe). Basically the whole tank is a giant, oxidative enviroment, and the reductive enviroment is too small in comparism

To quote, discuss...' I use bioballs and I dont buy into the 'Nitrate Factory' rubbish cus people who spout it off can't give a proper explination for the reason<<Does the above work for you>>. It just seems like a lemming response when people say they have a problem with nitrates and they use bioballs. Yet people who run a pure berlin method can and sometimes do end up with nitrates just as bad.<<Can be horrible in pure Berlin>>
Neither do I believe that the nitrifying/denitrifying bacteria are very close together and work like some kind of chain gang.<<Why not? Bear in mind we are talking very, very thin films here.>> If so you could say that using ozone causes nitrate levels to rise as it breaks ammonia down straight to nitrate and away from the LR in the same manner as bioballs.<<Never heard that one before. Ozone is used to 'crack' organic molecules, making higher charged molecules that are easier to skim>>

As a note, when I ran a nano, and also in my QT tank I use a cannister filter loaded with biomaterial. For sure it churned out nitrate, but with regular. large (50%) water changes, who cares?

[Horatii]

Ozone converts ammonium into nitrate - true. But how much ammonium do you run, generally, without the ozoniser ? If near to zero, running ozone is not likely to be an obvious source of nitrates.

If not near zero, oops !

Kim, ive only been keeping fish for about 19mths and reading about them for about 2yrs. I enjoy reading your posts and you are clearly very knowledgeable in reef keeping. I have problems trying to understand most things, especialy the chemistry side of things and have to read articles over and over to try and get my head around them. So please forgive me for my response as I feel like a student trying to teach the teacher and not knowing if im right or wrong. Its just my current understanding of things so far. :D

IMO, ammonia is in your water all the time but not to a tracable level that a off the shelf test kit will show. We add it with food and when we do water changes and fish constantly produce it. The bacteria that covers every surface area in the tank is very effective in breaking it down. The more surface area you provide, the quicker its broken down. Sand and bioballs have the largest surface area and break down ammonia/nitrites extremely well but your left with nitrates. So we add something to deal with the nitrates like a DSB, algae, nitrate reactors and more commonly, LR. The rock also has a large surface area and is quite capable of dealing with ammonia/nitrites with the added benifit of dealing with nitrates, so the need for bioballs or any other kind of mechanical filtration is not needed. But people still use them to increase the filtration.
So going back to the original question of wether this extra filtration hampers the denitrification with LR because the nitrification is taking place away from the LR, then the same could be said when using ozone.(?)

To quote, discuss...' I use bioballs and I dont buy into the 'Nitrate Factory' rubbish cus people who spout it off can't give a proper explination for the reason<<Does the above work for you>>.
Does your response work for me? No, although it does give some food for thought but doesn't explain why people say it produces extra nitrates and call it a nitrate factory. Although we might have different ideas on what the term 'Nitrate Factory' actually means? My understanding of the term and the way people use it is they are trying to imply that it produces extra nitrates. They way you have explained it is just that it produces nitrates in the way it had supposed to, by breaking down ammonia/nitrites resulting in nitrates. But your theory on thin films of bacteria and anaerobic being underneath it is saying that its possible for bioballs to be able to denitrify too? :confused:
It just seems like a lemming response when people say they have a problem with nitrates and they use bioballs. Yet people who run a pure berlin method can and sometimes do end up with nitrates just as bad.<<Can be horrible in pure Berlin>>
My first little reef(50gal) was almost pure Berlin method. Little skimmer, 20kg LR and an cannister filter for chem filtration and abit of floss in. For the first 5mths I had high nitrates but managed to keep it below 5ppm for the remaining 8mths it was running. Im not sure how I managed this but I put it down to my LR. It was overstocked(or at its limit), I only fed a small amount twice aday and only did a 20% water change every 2 weeks.

Neither do I believe that the nitrifying/denitrifying bacteria are very close together and work like some kind of chain gang.<<Why not? Bear in mind we are talking very, very thin films here.>>
Yes, its possible and could be the reason for my little reef doing so well after a period of time and giving these films time to develope.

If so you could say that using ozone causes nitrate levels to rise as it breaks ammonia down straight to nitrate and away from the LR in the same manner as bioballs.<<Never heard that one before. Ozone is used to 'crack' organic molecules, making higher charged molecules that are easier to skim>>
I dont know alot about ozone. I did read alittle about but got put off by the fact it can be harmful to us and I have children to think about so I focused my attention on other things. But from what I can remember im sure in a few articles it mentions that it breaks ammonia straight down to nitrates :confused:

As a note, when I ran a nano, and also in my QT tank I use a cannister filter loaded with biomaterial. For sure it churned out nitrate, but with regular. large (50%) water changes, who cares?
Alot of people seem to care and ask questions about nitrates and was the question that opened the thread. And I think most reef keepers would like to keep their nitrates down to at least 10ppm without the need to do water changes for the purpose of diluting high nitrates. People pay alot of money for LR in the belief that it is part of the main filtration that they need in reef tank. So if they are getting high nitrates they are bound to be curious and ask why.

[wayne in norway]

I'm going to try to build a simple answer that hangs together logically. If you have bioballs in a wetdry or whatever, these can only produce nitrates frmo the available ammonia/nitrite. They can't produce nitrate from 'fresh air and love'. At the end of the day I guess they're nitrate factories because their setup/enviroment only lends themselves to producing nitrates which are dumped back into the water column rather than being passed onto a layer of denitrafying bacteria.
I will confess I do not know for sure if dentrafication can occur in bioballs or if it ever does occur, but enough popular evidence seems to exist that it doesn't occur often, if it does. Some reasons for this might be that the whole enviroment in the wetdry/bioballs is just too aerobic, oxygen rich for the reductive reactions to take place. Other arguments might refer to the relatively smoothsurface of a bioball compared to the texture of live rock. It might be that this doesn't allow for thick bacterial films to occur - they are sheared off by passing water, and anaerobica bacteria are never established in large enough quantities, or for long enough. It might also be worth remembering that comapred to the oxidation of ammonia, the reduction of nitrate is quite a slow, weak process, so if you have equal quanitities of bacteria doing both, nitrate production will exceed removal. Thus you need an enviroment where relatively large numbers of anaerobic bacteria are neeeded, and the bioballs certainly don't allow for this.

I can't find any reference to ozone breaking down ammonia to nitrate. There's plenty on low levels of ozone cherging up some molecules and making them stick together better, and to thus skim out better.

I can't comment on berlin systems - I've seen them with, wothout horrible nitrate problems. If you don't have horrible nitrate problems then they are being removed somewhere. It seems these problems can develop almost overnight. I would wonder if that is due to the live rock, at a point in time, being choked by waste materials, and the dentrafication stopping at that time. Biofilms are sticky, and stick floc and debris to themselves

I chucked in the comment around my own system as a point that I'm not radically for/against bioballs - all these things have a palce as long as you try to understand what's going on in your own system. I personally like water changes, but that's as much as for organic waste removal for the stuff that doesn't enter the nitrogen cycle as for nitrate dilution.