Question Nitrogen Cycle In Acidic Water?

PubliusVA

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I've read in many places that beneficial bacteria go dormant and/or die off at pH levels below around 6. However, there are a lot of fish whose natural environment is more acidic than that. For example, on Seriously Fish the entries for some Boraras species (like chili rasbora) say that they are found in "very soft (negligible hardness), acidic (pH as low as 4.0) water," and the pH range for green neon tetras is given as 3.0 to 6.5!

How does the nitrogen cycle work in soft, acidic water environments like that? Or if it just doesn't, how is ammonia controlled? Just through absorption by plants?
 

jacob thompson

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It doesn’t at the low ph ammonia becomes ammonium which is abasicallg harmless to fish and then plants absorb all the excess ammonium before it can overload the ecosystem. Above 7 ph ammonium becomes ammonia which is deadly which is why the nitrogen cycle exists.
 
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PubliusVA

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Does that mean you don't have to worry about cycling a tank if you keep pH consistently below 6 and have fish that prefer acidic water?
 

jacob thompson

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Not in aquariums it’s basically impossible to plant it enough to make it 0 ammonium and ammonia. And if anything causes a increase of ph the ammonia would instantly become toxic to the fish. So you can set up a blackwater aquarium but you need to be 100% sure the ph never raises and plant it a lot.
 

LilHoodoo

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I had successfully fish-less cycled a 15gal tank recently; worked brilliantly in just under 2 weeks (with a cheater foam filter and an old filter element) ...so pleased!
Nothing to this "fish" stuff!
Got a used 20gal and began a fish-less cycle, @ 6.0ppm NH3/4, new substrate, and old pre-seeded foam filter, some ornaments out of a working tank...Took about a 2 weeks to test Ammonia @0.25 ...super!
Re-dosed to Ammonia to 4.0ppm - tank ammonia down to 0.25ppm in 24 hours! Then I tested NO2, was at 0.5ppm Repeated with the same results several times with the ammonia going to near 0ppm in 12 hours.You know that "almost kinda yellow or is it green" point of the API liquid test... ?
Clearly the Ammonia was under control but the Nitrate would take longer... The tank began processing the Ammonia in just 12 hours 4.0ppm to 0.25 or 0.0ppm but the Nitrate hung at 0.5ppm.
(NOW - Here comes how I messed it up)
- thinking I could accelerate the process I threw on a brand new Aquaclear50 HOB, and 3 large chunks of Mopani driftwood acquired at a local garage sale, which I brought home and boiled up before adding to the tank (I was thinking I'd get a head start on a 55gal I got for my birthday)
First test was OK; the ammonia seemed a little high like 0.5 in twelve hours - maybe I overdosed?
Next test was worse - looks like my bacteria was dying off! Day after day the Ammonia levels were growing - to the point where I stopped needing to re-dose BUT my NitrItes went back to 0.0 Baby Blue!
In blind faith I continued to re-dose as required and waited as the Ammonia spiked and Nitrites went to 0.0
OK - so now I've got a tank that won't come off 4.0ppm ammonia, has zero Nitrites, and incidentally the Nitrates NO3 are off the scale. Nuts.
So I sat there cursing the damned mysticism involved, (obviously this "fish" thing is harder than I thought) looking at my empty 55gal on the next stand in dread... and then noticed - this tank has taken on the hue of weak tea!
As has been pointed out in previous posts - my PH (and mine is at 6.0) is converting my Ammonia to Ammonium - I'm STARVING my bacteria. !
SO
My question is, short of taking out all the wood, flushing out the tank with a 100% water change, and start all over again with a 6.0ppm Ammonia dose, wadawydoo?
Thanks for any insights - LilHoodoo
 
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