Can extra biological filtration reduce nitrates?

[Crested]

Hey all, I recently saw a post about extra biological filtration (specifically using Marine Pure blocks) reducing nitrates. On the other hand, I have heard many people call this a nitrate factory. So I guess I was wondering what your experience has been with either the blocks or any other biological filtration product

 

[Hermie]

According to the tests I've seen, denitrification via media is more or less insignificant to non-existent. I am not saying that the science doesn't work, however the amount of denitrification that ceramic blocks or even live rocks perform is wayyyy overexaggerated and it's much much much much easier and faster to export nitrates via live plants like macroalgae or other uptake mechanisms. That's not to say there's no benefit to marine pure blocks or other ceramic media (or live rock): there is benefit, they are great places where Nitrification can take place. But they are not great for anaerobic/anoxic environments compared to the rate we need them to be.

 

[Crested]

According to the tests I've seen, denitrification via media is more or less insignificant to non-existent. I am not saying that the science doesn't work, however the amount of denitrification that ceramic blocks or even live rocks perform is wayyyy overexaggerated and it's much much much much easier and faster to export nitrates via live plants like macroalgae or other uptake mechanisms. That's not to say there's no benefit to marine pure blocks or other ceramic media (or live rock): there is benefit, they are great places where Nitrification can take place. But they are not great for anaerobic/anoxic environments compared to the rate we need them to be.

That's what I thought too, I just saw a post in a Facebook group about it and some people swore that their bio blocks were the reason for their low nitrates and it threw me off a little haha

 

[BZOFIQ]

According to the tests I've seen, denitrification via media is more or less insignificant to non-existent. I am not saying that the science doesn't work, however the amount of denitrification that ceramic blocks or even live rocks perform is wayyyy overexaggerated and it's much much much much easier and faster to export nitrates via live plants like macroalgae or other uptake mechanisms. That's not to say there's no benefit to marine pure blocks or other ceramic media (or live rock): there is benefit, they are great places where Nitrification can take place. But they are not great for anaerobic/anoxic environments compared to the rate we need them to be.

What about sulfur reactors? Do you feel the same about these as well. There are people who dose their tanks because nitrates are at zero.

 

[malacoda]

In my experience, denitrification through media is immense -- but it has to be proper media implemented in the proper way.

For example, I started my 24g with aquacultured Walt Smith (man-made) rock. For nearly a year I could not get my NO3 stay at or below 15ppm despite weekly water changes and light feeding. Within a week it would creep back up to 20, 25, then higher.

I added Seachem De-Nitrate (which is just very micro-porous rubble) passively in my sump. Still no change.

The problem: I wasn't using it the right way.

While trying to figure out why it wasn't working, I took a closer at the instructions on Seachem's website. That's when I realized it called for 20-50 gph of flow. So I put into a DIY reactor, ran 30 gph through it off of my return line, and BAM. Within 4 days my NO3 fell from 20 ppm to 1 ppm and has remained there rock steady for more than 2 years.

I even went skimmerless and only change my floss once a week. Still rock steady at 1ppm because the anaerobic bacteria population is now more than able to keep up with NO3 levels. (BTW - the tank has a 2" fine sand bed and I do not clean it.)

Bottom line: because of that media -- which is now getting the proper amount of flow (not too little and not too much) -- I use no mechanical filtration other than floss I change every 7-10 days. And I only have to do a 20% WC change once a month.

I posit that people who aren't seeing success with Marine Pure blocks or other such micro-porous media either have too little or too much flow passing through them for them to work properly.

This is one of the reasons why pukani has earned such a high reputation with old school reefers. It's micro-porosity is stellar for supporting anaerobic bacteria.

Just my two cents from what I've experienced in my own system.

 

[Hermie]

What about sulfur reactors? Do you feel the same about these as well. There are people who dose their tanks because nitrates are at zero.

That's a whole different ballgame. I have zero experience with them and have done little research. My impression is that they work and are effective.

While trying to figure out why it wasn't working, I took a closer at the instructions on Seachem's website. That's when I realized it called for 20-50 gph of flow. So I put into a DIY reactor, ran 30 gph through it off of my return line, and BAM. Within 4 days my NO3 fell from 20 ppm to 1 ppm and has remained there rock steady for more than 2 years.

I posit that people who aren't seeing success with Marine Pure blocks and such my not have enough flow through them to keep detritus from clogging them and/or to keep enough NO3 passing through in order to keep the anaerobic bacteria population healthy enough to do its job.

Just my two cents from what I've experienced in my own system.

It's definitely intriguing considering your results. A couple notes,

• what was the volume of your container? A small container of media with 20gph flow is a lot different than a 10 gallon tank receiving the same flow.
• were you sure that the water going into the container was "oxygen deprived" ? Anaerobic bacteria generally only activates when they cannot perform aerobic functions which they prefer.

I like your anecdote however I can't put much faith in it at this point... enjoying the discussion though.

 

[malacoda]

It's definitely intriguing considering your results. A couple notes,

• what was the volume of your container? A small container of media with 20gph flow is a lot different than a 10 gallon tank receiving the same flow.
• were you sure that the water going into the container was "oxygen deprived" ?

Before using the container, the De*Nitrate was sitting in a mesh bag in my sump. The sump has about ~3.5 gallons of water in it when the system is running (e.g. when return pump is running). And my system was turning over about 120 ghp through the sump.

Container was originally a DIY reactor made from a 32oz mayo jar. (Recently I replaced with a shortened 2 Little Fishes Phosban 15 reactor due some epoxy I used to assemble the DIY jar finally giving out.)

It was the same volume of De*Nitrate rubble in both instances -- I merely dumped the rubble from the mesh bag into the reactor.

It is also the ONLY change I made at the time of the NO3 drop. As a former mechanical and quality assurance engineer I know to avoid testing more than one variable or system change at any give time if at all possible.

Anaerobic bacteria generally only activates when they cannot perform aerobic functions which they prefer.

Kind of goes back to my initial comment: "In my experience, denitrification through media is immense -- but it has to be proper media implemented in the proper way."

Porosity of the media, too little flow, to much flow -- all can have an impact.

If any of them are not present to an appropriate degree for the given system, denitrification from media probably will be negligible.

If they are in proper balance though, again at least in my experience, the impact can be quite significant.

I'm in the process of setting up a 65g, and plan on repeating the set-up type. Same type of rock. And then, if NO3 is above 1-5 ppm, will follow up with De*Nitrate in a reactor fed of the return line. Will be a good opportunity for me to see if the results are repeatable.