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  Topic Review (Newest First)
Today 01:36 PM
hitmanx 3 years to the day and I am still on the edge of my seat!

Did you ever end up melting the samples?
02-06-2013 10:03 PM
lochaber
Quote:
Originally Posted by VAtanks View Post
The only thing I can say for sure is the channels or pores under microscope are very similar.

I would think this would be the important part for it's purpose as biomedia. Even if it isn't exactly pumice, if it is similar enough, then people could probably get similar results using much cheaper horticultural pumice.
02-06-2013 02:43 AM
VAtanks Unfortunately I am not able to tell, both are silica based but since pumice has such a huge range between 78ish percent all the way to about 89 percent. I can not tell, at this point I couldnt even difinitively say my BBQ grill scrubbers are pumice. and am considering removing them. The only thing I can say for sure is the channels or pores under microscope are very similar. El cheapo microscope though so at this point my two samples are in the hands of a geologist adjunct professor. It was suggested I heat both samples to about 800 degrees and if they flow then they do belong to the glass family of compounds.....but that wouldn't answer is Matrix pumice....
02-05-2013 11:40 AM
CrypticLifeStyle
Quote:
Originally Posted by VAtanks View Post
CrypticLifestyle, I will find that answer out for you tomorrow night in my Chemlab class, I will take one piece of Matrix and one BBq scrubber into lab class with me and examine it and hopefully photograph it adnd I will post the findings here, I might be able to get some grad students to chem analize it for us too.
That would be awesome. This has been of much great debate. Some solid scientific answers to a degree will open up some of the mystery.
02-05-2013 12:31 AM
Darkblade48
Quote:
Originally Posted by VAtanks View Post
Physics major/Engineer...so chem baffles me. Is DNRA bacterial related or is it just a natural chemical reaction based on water conditions?
As you mentioned below, it is bacterial mediated. It occurs in facultative aerobic bacteria, so it really only occurs in the absence of oxygen (anaerobic bacteria).

Quote:
Originally Posted by VAtanks View Post
...my follow on question would be, if this is naturally occuring in nature has it been established in a tank? would seem to me outside of trace elements needing to be refreshed would almost eliminate the need for water changes?
For your second question, it is a very difficult one

Some things that happen in test conditions, do not necessarily happen in nature, and vice versa. On top of that, since nature is not controllable, it makes things even more complicated.

As I mentioned, DNRA is much less common than denitrification. The amounts of ammonia/ammonium being produced would be much less than nitrites/nitrous oxides that would be produced through the denitrification pathway.

So, let's assume that nitrites are being produced; the amount of it being produced would be dependent on the number of facultative aerobic bacteria, which would be in turn based on the amount of anaerobic space there is in the Matrix biomedia (assuming it exists). This surface area would be greatly outmatched by the surface area that exists in aerobic conditions, so nitrification (production of nitrates) would be much more favoured.

With nitrates being produced, water changes will be required (assuming you do not have a planted aquarium whereby plants are uptaking nitrates...).

To my knowledge, in reef aquariums, the production of nitrates is slowed down through the addition/construction of a plenum.
02-05-2013 12:23 AM
VAtanks Seems its strictly bacterial related only and only in an anaerobic environment specifically pseudomonas and clostridium bacteria. which brings us back to the zero air zone in the matrix, but my follow on question would be, if this is naturally occuring in nature has it been established in a tank? would seem to me outside of trace elements needing to be refreshed would almost eliminate the need for water changes?
02-05-2013 12:13 AM
VAtanks Physics major/Engineer...so chem baffles me. Is DNRA bacterial related or is it just a natural chemical reaction based on water conditions?
02-05-2013 12:03 AM
Darkblade48
Quote:
Originally Posted by VAtanks View Post
So basically the end result would be N2 in a crystaline form at the soil/water contact point as a result of DNRA? I did find a few more articles one from a text book from 07, still relavant though
Biogeochemistry
January 2008, Volume 87, Issue 1, pp 99-111
http://link.springer.com/article/10....9171-6?LI=true

Good job Dark, I happen to have gotten into fish tanks not for their beauty but for the science...thanks for fanning the flame.
Nitrogen is not crystalline, nor is it the end product of DNRA. The end result of DNRA is ammonia/ammonium, depending on pH.

Regarding your link to the article (not a textbook), it points out that "the importance of DNRA in freshwater sediments appears to be minor relative to DNF."

As I previously mentioned, DNRA is probably rarer than denitrification.
02-04-2013 11:14 PM
VAtanks So basically the end result would be N2 in a crystaline form at the soil/water contact point as a result of DNRA? I did find a few more articles one from a text book from 07, still relavant though
Biogeochemistry
January 2008, Volume 87, Issue 1, pp 99-111
http://link.springer.com/article/10....9171-6?LI=true

Good job Dark, I happen to have gotten into fish tanks not for their beauty but for the science...thanks for fanning the flame.
02-04-2013 11:00 PM
Darkblade48 Those images show that the process referred to as denitrification reduces nitrates to nitrous oxide (through nitrite) and/or nitrogen gas.

Direct reduction of nitrates to ammonium (ammonia) is done by a process known as "Dissimilatory nitrate reduction to ammonium (DNRA)"

Here is some good reading for more information regarding DNRA.

Quote:
Sgouridis F, Heppell CM, Wharton G, Lansdown K, Trimmer M. Denitrification and dissimilatory nitrate reduction to ammonium (DNRA) in a temperate re-connected floodplain. Water Res. 2011 Oct 15;45(16):4909-22. doi: 10.1016/j.watres.2011.06.037. Epub 2011 Jul 8.

Nizzoli D, Carraro E, Nigro V, Viaroli P. Effect of organic enrichment and thermal regime on denitrification and dissimilatory nitrate reduction to ammonium (DNRA) in hypolimnetic sediments of two lowland lakes. Water Res. 2010 May;44(9):2715-24. doi: 10.1016/j.watres.2010.02.002. Epub 2010 Feb 7.
02-04-2013 10:25 PM
VAtanks
02-04-2013 10:24 PM
VAtanks
Pictures easier than typing

02-04-2013 09:16 PM
Darkblade48
Quote:
Originally Posted by VAtanks View Post
CrypticLifestyle, I will find that answer out for you tomorrow night in my Chemlab class, I will take one piece of Matrix and one BBq scrubber into lab class with me and examine it and hopefully photograph it adnd I will post the findings here, I might be able to get some grad students to chem analize it for us too.
I'll be waiting for mass spectrometry results then. But seriously, I don't think you'll find many helpful graduate students, trust me, I know from experience. I was one of them

Quote:
Originally Posted by exv152 View Post
I think, and I'm not an expert by any means, the actual process in denitrification involves bacteria reducing nitrates to nitrites, and then reducing that to two things; nitrogen gas and ammonia. The part that's converted back to ammonia will get used again by the bb, but the part turned into nitrogen gas is not usable and is lost to the atmosphere.
Neither am I, my research had nothing to do with soil bacteria

A quick search on Pubmed reveals that denitrification generally involves bacteria reducing nitrates to nitrogen through the nitrite intermediary. There are some bacteria that just leave it at the nitrite step (meaning it would be available for beneficial bacteria), while some take it all the way to nitrogen gas.

While direct reduction to ammonium from nitrates is possible, apparently it is rarer than going through the nitrite intermediate.

I still find it hard to believe that an anaerobic environment could exist in a canister filter with good flow and porous media. Now, if it were a plenum, I could see it happening.
02-04-2013 06:59 PM
exv152
Quote:
Originally Posted by Darkblade48 View Post
Yes, I was thinking the same thing; somehow, the media must create localized anaerobic spots for denitrification to occur.

However, what would be the purpose (if anaerobic bacteria truly are present)? Denitrification would take the nitrates that are produced by the aerobic bacteria, and convert back to nitrites...which are then converted back to nitrates by the aerobic bacteria.

On top of this, the aerobic bacteria would be much in excess compared to the anaerobic bacteria, meaning nitrification would be very favoured.
I think, and I'm not an expert by any means, the actual process in denitrification involves bacteria reducing nitrates to nitrites, and then reducing that to two things; nitrogen gas and ammonia. The part that's converted back to ammonia will get used again by the bb, but the part turned into nitrogen gas is not usable and is lost to the atmosphere.
02-04-2013 06:07 PM
VAtanks CrypticLifestyle, I will find that answer out for you tomorrow night in my Chemlab class, I will take one piece of Matrix and one BBq scrubber into lab class with me and examine it and hopefully photograph it adnd I will post the findings here, I might be able to get some grad students to chem analize it for us too.
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