Audemars

during the nitrogen cycle, when my LR is in place, i read that when the LR is introduced it can cause a intense amonia spike and kill some of the nitrofication/dentrofication bacterias. my question is that if this is the case then would doing deep water changes help reduce nitrogen lvls and save some of the good bacteria that came w/ the LR?
are you supposed to do water changes at all during a nitro cycle other than topping off?
lastly i read that you should not use a filter in tandem with a biofilter like LR and that doing so can lead to elevated nitrogen? true?

thank you,
-Aud

Naeusu

That's a confusing statement....it's true LR does most of my filtering but i still needed to get a sump for my systems in order to properly keep my levels in place.

locoyo386

Hi there, here is my attempt to answear your question;

First: The Nitrogen Cycle;
For our sake I will kep it simple and not go into the chemistry that takes place during this process, and I am going to keep it on the nitrification process only. When our tanks are set from scratch, they undergo a process that we call nitrogen cycle or "cycling the tank". The first thing that needs to happen is we need to introduce ammonia to get it started. This can be done in many different ways, some of the most popular ways are; using live rock, dead cocktail shrimp, "ghost" feeding. Basically anything that can breack down into ammonia will work. Once the ammonia is introduce than you deed to add water movement to circulate the ammonia throughout the tank. Than a bacteria called "Nitrosomonas" grows and convertes ammonia into nitrites. The amount of ammonia will determine how much bacteria will grow. Once nitrites are present in the water, another bacteria, called "Nitrobacter", starts to grow. This bacteria will convert nitrites into nitrates. This is were we will end, we will not go into the denitrification process that takes affect once nitrates are present (unless you want to).

Secon: Filtration during cycling of tank;
The filtration is irrelevant to the cycling of the tank. The only thing is that both bacteria responsible for the cycling live on the surfaces inside the tank. All surfaces in contact with water with provide a place for bacteria to colonoze, including the filters. I prefer to run the filter without any media (carbon, filter pad, etc.), that way the bacteria will not grow in these areas, and you do not have to depend on them for your bio-filter.

Third: Llive Rock;
When live rock is used to cycle the tank, you are depending on live things dieing. The living things die becaue there is no food for them, this will introduce ammonia into the tank and start the cycle. The spike that happens in ammonia depends on how much living matter decays.

Fourth: Water changes;
I would not recomend water changes during the cycling of the tank, specially if there are no living fish, invertibrates or corals. Reason being that you have to let the bacteria grow, and their gorwth is dependent on the ammonia and nitrites. Once you the tank has reached a stable cycle than you can do a water change.

Fith: Nitrogen;
I have never read anywhere that states that nitrifying or denitrifying bacteria die due to elevated nitrogen levels. I would not concern myself with this. Also if you have a good "water sruface" movement, you will have a good gas exchange. This will allow notrogen gases to escape the tank.

If you have anyfurther questions let me know.

David C

Good explanation Locoyo. It was discussed in another thread that extreme levels of ammonia can kill off the bacteria, but these levels are improbable if you are adding the LR to a fresh tank for cycling. It was more concerned with a case where using TSS after a tank already had a level around 8ppm and the bacteria was killed off.

Filters don't function the same in SW tanks as FW. The LR actually functions as the biofilter.

Dave

locoyo386

Thanks Dave