Denitrfication

[Cory]

What would happen if i took my tanks water, and sealed it up for a week, then added it back to my tank after aeration for a few days? Would no3 be zero? Anything bad inside?

 

[Spare time]

No you have to get the bacteria from somewhere do to that since the only places they could live in your tanks is deep within a rock or media and at the bottom of a rarely disturbed sandbed. They don't live in the water column either (at least from my understanding). They could also end up just producing some form of sulfer and nitrite if you had them in there in the first place.

 

[Randy Holmes-Farley]

The answer will depend on many things, such as the level of organics in the water. It may become anaerobic and produce hydrogen sulfide.

 

[Cory]

But could this be okay to use provided I areated it? Hydrogen sulfide can offgas, what would happen? Low alkalinity and ph?

 

[Randy Holmes-Farley]

But could this be okay to use provided I areated it? Hydrogen sulfide can offgas, what would happen? Low alkalinity and ph?

Much of the "hydrogen sulfide" will not off gas, but be present as HS-. This sounds like a poor plan to me.

 

[Cory]

Much of the "hydrogen sulfide" will not off gas, but be present as HS-. This sounds like a poor plan to me.

Okay thanks. Im trying to find a good way to remove no3. My no3 always maxes out on saliferts no3 kit (100ppm max) and I read an article saying nitrate reduces skeletogenisis rates greatly. Problem is I dont have a sand bed its a bb tank. So my options are refugiums, or carbon dosing. Both of them seem inferior to just plain old denitrfication when you want to grow coral and dont water change much. Maybe i should just add sand.

 

[tnw50cal]

You have rocks in your tank don't you? Do you have any Biomedia in your sump? Those are places denitrification bacteria live in a barebottom tank. Have you thought about adding bacteria(like microbacter 7)? Water changes help remove NO3 too.

 

[Cory]

You have rocks in your tank don't you? Do you have any Biomedia in your sump? Those are places denitrification bacteria live in a barebottom tank. Have you thought about adding bacteria(like microbacter 7)? Water changes help remove NO3 too.

Yes i have rocks. To be honest im not sure if its ever been proven that live rock has any great ability to denitrate. I dont use those bricks either because they either add aluminum, or silicate at uncontrolled rates. Water changes may be the option. But i want to do a 90% water change, and gotta buy a container that holds 100 gallons at least.

 

[Dan_P]

What would happen if i took my tanks water, and sealed it up for a week, then added it back to my tank after aeration for a few days? Would no3 be zero? Anything bad inside?

Great question!

That would be the equivalent to running a very large scale biological oxygen demand for 7 days, i.e, a BOD7. The amount of oxygen consumed depends on how much dissolved organic carbon is in the water. For my aquarium, that translates to very little oxygen consumed in 5 days. There just isn’t enough DOC to feed the bacteria.

In answer to your question, I suspect that nitrates will be unaffected because the amount of organic carbon in any “healthy” aquarium Is too low to enable much bacteria growth and therefore little demand for nitrate. You can try your experiment by placing a sample of tank water in a capped vial and measuring the nitrate after a week.

There is a situation where tank water actually generates nitrate when aerated for weeks. I think in that situation, organisms in the water are dying and being digested.

 

[Cory]

Great question!

That would be the equivalent to running a very large scale biological oxygen demand for 7 days, i.e, a BOD7. The amount of oxygen consumed depends on how much dissolved organic carbon is in the water. For my aquarium, that translates to very little oxygen consumed in 5 days. There just isn’t enough DOC to feed the bacteria.

In answer to your question, I suspect that nitrates will be unaffected because the amount of organic carbon in any “healthy” aquarium Is too low to enable much bacteria growth and therefore little demand for nitrate. You can try your experiment by placing a sample of tank water in a capped vial and measuring the nitrate after a week.

There is a situation where tank water actually generates nitrate when aerated for weeks. I think in that situation, organisms in the water are dying and being digested.

I may try this vial experiment and see what happens. Ill actually try two, one with vinegar added and one without. Thanks!

 

[Dan_P]

I may try this vial experiment and see what happens. Ill actually try two, one with vinegar added and one without. Thanks!

You are actually doing an experiment I have been thinking about. Using small scale dosing observation to predict how the aquarium will respond. I would be interested in hearing your results. I wonder if @taricha has tried any variation of this experiment?

 

[Randy Holmes-Farley]

I agree that if nitrate is that high that it is unlikely to be removed without adding organic carbon, and that H2S won’t likely be an issue. If you add organic carbon in sufficient amounts to reduce all nitrate, then H2S production becomes a significant risk again.

 

[chipmunkofdoom2]

So my options are refugiums, or carbon dosing. Both of them seem inferior to just plain old denitrfication when you want to grow coral and dont water change much.

Out of curiosity, why do you feel these methods are inferior for nitrate control specifically with regards to systems with fewer water changes?

 

[Cory]

Out of curiosity, why do you feel these methods are inferior for nitrate control specifically with regards to systems with fewer water changes?

Denitrfication doesnt require high powered lighting or dosing iron/potassium like a refugium does. It also doesnt require you to throw away macroalgae as the no3 from denitrfication off gasses.

 

[taricha]

You are actually doing an experiment I have been thinking about. Using small scale dosing observation to predict how the aquarium will respond. I would be interested in hearing your results. I wonder if @taricha has tried any variation of this experiment?

I haven't tried it for the purpose of predicting a carbon dose regime on a main system, but...
Storing tank water (aerated) for days or a couple of weeks:
In my case, NO3 and PO4 decrease gradually, then level off after a few (~5) days. This likely represents the organics in my water that can be broken down. This carbon source is kind of a middle ground in terms of digestibility. Vinegar or Vodka would get consumed much faster, other forms of carbon may be totally indigestible.
After that point (~5 days in my case) NO3 and PO4 reductions are very very small. Simply storing/aerating tank water doesn't bring down high nitrate enough to solve any problems.

If I carbon dose during the hold/aeration time, then I get PO4 and NO3 to decrease all the way until one is depleted. I also see biomass growth of a couple of forms: cloudy water early, and more slowly, debris/film accumulation. I suppose if this were done for 2 weeks, the cloudiness cleared, and debris/film accumulation left at the bottom when the water gets removed from the container, then I guess it's kinda doing what @Cory wants.