Nitrate and ????

[jjohnwm]

That's one of the benefits of using nitrate level as a barometer of water condition. Aside from the fact that nitrates are measurable using simple, inexpensive test kits that are accessible to and useable by almost anyone, nitrates are produced in a properly cycled aquarium as the end result of the decomposition of all sorts of organic matter. All of those vaguely-referenced hormones and pheromones and other compounds are produced and excreted by the fish themselves. Nitrates, on the other hand, simply indicate that some type of organic matter has undergone bacterial decomposition. It might be fish waste, but could just as easily be uneaten food, decaying plant matter, a dead fish or infertile eggs. Doesn't matter where it came from, it still shows that a water change is required...and that change will also tend to the mystery compounds too.

There are plenty of feeding videos and pics that show how unbelievably sloppy many people are when feeding their fish. Food everywhere, piled on the substrate (but it's okay, because they are planning on doing a water change tomorrow or the next day and will vacuum it all up!). I'd bet good money that the bulk of the nitrate produced in many tanks comes from uneaten food.

Dirty water is dirty water, and needs to be changed.

 

[A201]

Just had the water from my heavily over stocked 120 gal. tested. It had been two years from the last test. Results: 0 -Ammonia, 0 - Nitrite, < 20 Nitrate, PH 8.2. Just two modified Emperor 400's for filtration.
I generously feed the fish once or twice a day. 35% - 50% weekly WC.
Although I was very happy & quite surprised with the low nitrate reading,
I'm not really overly concerned with a reasonably elevated nitrate level, say
40 - 50 ppm.
Not to open a can of worms, but I believe the BB residing in my deep gravel substrate has a lot to do with the low nitrates.

 

[RD.]

FYI - deep gravel substrate does not reduce nitrate, if anything it becomes a nitrate factory, increasing nitrate levels.

Deep sand beds, used in some marine systems, have demonstrated nitrate reduction.

 

[A201]

Yeah, I'm certainly no scientist and don't know how subterranean denitrification can or cannot work.
Over the years several "Naturalist" fishkeepers have suggested deep
gravel beds & no gravel vacs as a way of achieving excellent water parameters.
I've obviously taken the deep substrate advice & haven't gravel vacuumed in several years. Of course I consider a weekly substantial WC a must.
I've viewed videos of commercial fish breeder "Lucas Betz". His tank management philosophy is very similar to mine. Although his expertise & skills are far more advanced. Lol.

 

[RD.]

Gravel does not work as 02 will find its way down to the the bottom layer, hence no anaerobic zones. Deep sand beds (DSB) can work (this has mostly fallen out of favor even with marine keepers) due to the very fine particle size of sand, which means that 3-4" will often suffice to achieve an anaerobic zone, if left undisturbed by us & the fish. Even with very fine gravel, one would require 10-12", maybe more, to achieve the same as a 3-4" layer of sand. It's simply not practical to use gravel, well unless you have some VERY deep tanks.

Not my words, but this explains the process.

Biological denitrification is an anaerobic respiration reaction in which nitrate (NO3) is reduced. Denitrifying bacteria are aerobic autotrophs or heterotrophs that can switch to anaerobic growth when nitrate is used as an electron acceptor (Bitton 1994). Denitrification can occur by two pathways. The dissimilative nitrate reduction pathway requires anoxic conditions and results in the liberation of nitrogen gas from the water column (Reed et al. 1988; Madigan et al. 1997). Under aerobic conditions denitrification results in the assimilative pathway or accumulation of nitrogen into biomass (Bitton 1994; Madigan et al. 1997). It is desirable to encourage the dissimilative pathway of denitrification so that nitrogen may be completely removed from the system in gaseous form rather than simply recycled through the system in biomass. In order for this to occur, there must be insufficient molecular or dissolved oxygen present so that the bacteria use the nitrate rather than the oxygen. The rate of the denitrification reaction is relatively fast when there is no free oxygen present (< 0.5 mg/l is ideal). The denitrification rate drops to zero when the dissolved oxygen level reaches 2.0 mg/l.

 

[RD.]

..... and there are certain products that claim to remove nitrates via anaerobic denitrification , due to their pore size. I have no idea how well this type of media works, but I suspect that large water changes work a LOT better. I have some Seachem Matrix as part of my bio-filters for the past 15 yrs or so, but I doubt it adds a whole lot to the de-nitrification process.

Seachem - de❊nitrate

Seachem - Matrix

 

[esoxlucius]

..... and there are certain products that claim to remove nitrates via anaerobic denitrification , due to their pore size. I have no idea how well this type of media works, but I suspect that large water changes work a LOT better. I have some Seachem Matrix as part of my bio-filters for the past 15 yrs or so, but I doubt it adds a whole lot to the de-nitrification process.

Seachem - de❊nitrate

Seachem - Matrix

I'm puzzled, not that it takes a lot, lol.

If the denitrification process requires less than 2ppm of dissolved oxygen to get kick-started, then how does the nitrate molecule reach these areas to be processed, but the oxygen molecule can't, which would stop the process. Surely the oxygen and nitrate are side by side in the water column. Anywhere the nitrate can get to, then so can the oxygen.

If nitrate can access these "deep bed" areas to be processed, then so can the oxygen, to stop the process. Seems like a really complex balancing act, and for little reward when all said and done.

 

[Rocksor]

I'm puzzled, not that it takes a lot, lol.

If the denitrification process requires less than 2ppm of dissolved oxygen to get kick-started, then how does the nitrate molecule reach these areas to be processed, but the oxygen molecule can't, which would stop the process. Surely the oxygen and nitrate are side by side in the water column. Anywhere the nitrate can get to, then so can the oxygen.

If nitrate can access these "deep bed" areas to be processed, then so can the oxygen, to stop the process. Seems like a really complex balancing act, and for little reward when all said and done.

I was under the assumption that the oxygen gets "eaten" by aerobic bacteria on the way to the anaerobic area. It would be like a denitrator filter with low flow.

 

[duanes]

I like to draw on Reef hobbyist technology for many ideas because it is usually way ahead , and much more intricately woven than the haphazard approach much of the fresh water hobby takes.
So in the 90s after Bob Fenner extolled the advantages of a deep sand bed, and Bob Goeman's added plenums to the mix, creating anoxic areas for nitrate reduction in a tank, I tried both, but for me , with only limited success.
The expense and fidgeting needed for mixing the salt and other chemicals in the reef water hobby, just wasn't practical for the nitrate reduction that simple 10 minute water changes a few times a week could provide, especially in the specific reduction goals of 5ppm I wanted.
And because cichlids are my obsession, the digging they do, tends to unearth and disrupt the conditions needed to maintain the anoxic conditions required to be effective.
I never kept up on, or found practical use for the concept.
Doesn't mean others won't, it just means it didn't; for me.

 

[markstrimaran]

About the pheromones, in my coed over stocked African Cichild tank. Unless the females are active laying eggs, the males generally leave them alone. As far as nitrates, I grow alot of algea, 350 watts worth 12 hours a day, plus 60 in the algea scrubber 24/7. The scrubber grows about 8 ounces per week( drained by volume), The fish graze on the 350 watt side, So I am not sure how many ounces grow their each week, maybe 16 ounces. Water change or not, once the nitrates, reach into the 20ppm blue green algea starts to smoother everything., and the lights go off for 3 days, as the WC increases to daily for a week. Tried every thing except bleach and antibiotics.
I agree in water changes, I am just experimenting. So far I have not been doing water changes, as I am testing the potency of bio char, mostly to figure out how much, I need and how often to change it. I have very little bio media for my tank as I want the algea to absorb all the ammonia, and skip the whole Nitrogen cycle.
Then the algea scrubber and the bio char keep the ph very consistent. I also have no substrate, just tile and lots of flow. With a sump. with lots of mechanical filtration, and biochar.