Anaerobic Bacteria in Freshwater Aquariums?

[Toby_H]

I work in wastewater treatment...

I've heard you say that before and have made a mental note of it... and thus appreciate/respect your input when I am rambling about Bio Filtration...

So based on your experience in waste water treatment... adapted to your understanding of home aquaria... complimented by your personal experience in home aquaria...

Do you think Bio Media such as Matrix can actually cater to anaerobic bacteria when used in a typical filtration situation (such as in a baseket in a canister/sump/HOB)?

 

[12 Volt Man]

Do you think Bio Media such as Matrix can actually cater to anaerobic bacteria when used in a typical filtration situation (such as in a baseket in a canister/sump/HOB)?

no. reason being, if you have a decent flow rate, you have lots of dissolved oxygen in the local environment.

the flow rate would have to be super low to create an environment with very low DO (aerobic bacteria would have to use up the DO first, and it would not be replenished fast enough because the flow rate is low). these aerobic bacteria would not survive (unless they were facultative aerobes - bacteria that can exist in aerobic or anaerobic conditions) and anaerobic bacteria would begin to thrive.

you won't get that with normal flow in a canister or sump.

 

[Toby_H]

From my understanding... their 'claim' is that the anaerobic bacteria live at the center of the nugget... so the water enters the nuget with DO... the bacteria on the outer portions of the nugget use the DO... and the water at the center is then anaerobic...

While I understand that "logic"... or train of thought... based on my understanding of bacteria, ammonia and home aquaria... it is grossly exagerated... the tiny bit of bacteria that actually lives in the outter portions of the bio media isn't going to use up anywhere near all of the DO in the water...


But I want to hear the opinions of other experienced / educated hobbyists as well...

 

[12 Volt Man]

not only that, you have a tiny fraction of the overall bacterial population dentrifying nitrate to nitrogen gas.

chances are, that tiny population isn't going to nitrify to a level that you will even pick up with conventional test kits..

I mean, if you have 25 mg/L nitrate (an average level in most home tanks) and hardly any anaerobic bacteria to break it down..your not going to see any benefit in your tank..

 

[Noto]

from what I understand, denitrification produces a few different gasses depending on the specific anaerobic bacteria involved.

not all anaerobic bacteria will produce hydrogen sulphide, only those that reduce (feed) on sulphur compounds can.

some of the gases that can be liberated during denitrification are:

Nitrogen gas
Nitrous oxide
Hydrogen Sulphide


most of the time, the bubbles that you see are not hydrogen sulphide, but nitrogen gas.

I work in wastewater treatment, and in the settling tanks, when the sludge blanket at the bottom gets too thick, we get bubbles of nitrogen gas coming up via the denitrification taking place at the bottom of the tank, since the blanket has little to no D.O in it.

Thanks for that. I figured H2S wasn't a major component of the gas, since its odor is detectable at very minute concentrations.

 

[dwilder]

i think matrix makes a decent bb media i see that they claim its from the pour size and structure that in the same filter it can support anaerobic bacteria i dont really see how, it may be able to in very small amounts enough to say it does but probably not enough to make a difference im sure they must have some data to support this has anyone asked yet

 

[tcarswell]

I have never noticed a difference on my oscar tank I run seachem matrix in a fluval 405. No measurable difference in Nitrates..... yet its been about 2 1/2 months.

 

[sostoudt]

no. reason being, if you have a decent flow rate, you have lots of dissolved oxygen in the local environment.

the flow rate would have to be super low to create an environment with very low DO (aerobic bacteria would have to use up the DO first, and it would not be replenished fast enough because the flow rate is low). these aerobic bacteria would not survive (unless they were facultative aerobes - bacteria that can exist in aerobic or anaerobic conditions) and anaerobic bacteria would begin to thrive.

you won't get that with normal flow in a canister or sump.

makes sense

side note stability or whatever seachem sells as a bb supplement is supposed to be facultative

 

[Toby_H]

facultative - bacteria that can grow in aerobic or anaerobic conditions (with or without oxygen)

Wikipedia says - http://en.wikipedia.org/wiki/Denitrifying_bacteria

Putting a part of that first paragraph into my own (simplier) wording...

There are facultative bacteria that process oxygen or nitrate... when oxygen is present they use oxygen, when oxygen is not present and nitrate is, they will then settle for nitrates...

So while these can scientifically be referred to as "denitrating bacteria"... in our systems that are saturated with Dissolved Oxygen, they will not process nitrate...

While I cannot make any concrete statements about what is in Stability... simply stating they use facultative bacteria doesn't mean anything impressive...

 

[sostoudt]

but they would be able to be used in a slow reactor or canister setup like 12 volt was talking about. its not what your looking for as in you just drop in super porous media in the regular filter. but i believe it would work just as good as a coil denitrator, with the turnover set correctly. personally i like the idea of the time water is in anaerobic zone a short as possible while still reasonably reducing nitrates. if the water becomes void of nitrates the bacteria will switch to sulfur(if they can) and create hydrogen sulfide.

article about hydrogen sulfide in saltwater aquaria, i believe most of the information is more or less accurate for freshwater also http://reefkeeping.com/issues/2005-12/rhf/index.php#14

your probably hoping for to much, if your looking for drop and go bio media in freshwater. if the ultra porous media do have anerobic areas i believe the areas to be very small and have very small turn over rate of water through them(even slower then a coil denitrator). so you would need a large amount media to effectively offset water changes. i suggest trying plant filtration or chemical filtration to reduce nitrates.

if you wish to do explore anerobic filtration, i recommend actively taking measure to lower oxygen concentrations in the filter area. such as enclosed slow flow filters or perhaps explore reverse deep sand beds(never seen these in freshwater but would probably work with flowrate adjusted correctly).