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Discussion Starter · #1 ·
I've been reading up a bit on the issue of whether Ammonia or Nitrate is the more beneficial form of N to a planted tank.

I've gathered that Ammonia may be better because it is the form of Nitrogen most readily-usable by plants. I've also seen that some think algae seems to be more favored with NH4 over NO3. We all know NH4 is more toxic to fish...

The reason I ask is because I am in limbo as to how heavily I want to rely on the biologic capacity of my filter. I was thinking I'd eventually remove most of the biomedia over time, as bacteria no doubt will colonize every surface inside the tank anyway. With alot of plants and small-grained substrate, the contribution by the filter may become negligible anyway...and NH4 to NO3 conversion largely unavoidable.

What are your thoughts? Is it relatively unrealistic to assume ammonia can be naturally available to plants for very long? If we can determine ammonia is preferable to nitrate from a plant standpoint, is it realistic to think plants can compete with bacteria?

All that aside, unless there is a pretty large fish load, is external biologic filtration even that important?
 

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Discussion Starter · #7 ·
Thanks for the thoughtful replies, guys.

IIRC, ammonia will stay as ammonium at acid pH. With CO2 injection, I don't think a drift toward alkaline pH is much of a worry - but I do know that "stuff" happens.

I will still be using the filter for (at least) mechanical filtration and water movement, but just wasn't sure whether the other compartment (Eheim 2224) would be better used with something other than biomedia. Perhaps some sort of buffer - like maybe a cup of dolomite or crushed coral to keep the hardness from getting too low. At a pH around 7, that stuff isn't that soluble, so I wouldn't anticipate much worry about pH getting too high.

I would assume the mechanical portion of ceramic rings will also serve some bio functionality...
 

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Discussion Starter · #9 ·
Yes for sure, but what I mean to say is that I don't anticipate that using something in lieu of the official biomedia is going to significantly compromise the biological capacity of the system. I would just as soon use something that serves a purpose other than providing a bunch of surface area for bacteria to colonize. Preventing bacterial colonization is largely unavoidable other than moderating how much surface area exists in the system, and of course, the fish load. If there is a low fish load, the bacterial population will be at a lower equilibrium with their "food" supply (ammonia/nitrite). That's why I partly think that a big time die-off situation may not save you even if you have lots of biomedia. It will take a while for the bacterial population to increase with the increased nutrients. You could basically think of it as another cycle, though it would be shorter in duration (until the nutrient levels start to return to "normal").

I do realize that biomedia in an area of high flow (filter chamber) would be most efficient at delaing with nutrients, whereas bacteria on in-tank surfaces will come into contact with a given volume of water much less often than 2 or 3+ times per hour (as in the filter).

Other than the filter, I will probably add a small powerhead as well to make sure there is adequate circulation in the tank itself.
 

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Discussion Starter · #12 ·
Shane,

If you have time, you may find this article interesting:

http://www.aquabotanic.com/plants_and_biological_filtration.htm

I have read several sources confirming that NO3 is essentially converted to ammonium by the plant after uptake.
As taken from the link: "Plants, algae, and all photosynthesizing organisms use the nitrogen from ammonia- not nitrates- to produce their proteins. If the plant takes up nitrate, it must first be converted to ammonium in an energy-requiring process called 'nitrate reduction'. Nitrate reduction in plants appears to be the mirror image of the bacterial process of nitrification."

If plants can get their nitrogen in the form of ammonium, they expend less energy, as it's already usable. If it's nitrate, they have to expend the energy to convert it. This is not to say that presence of only nitrate (and lack of ammonium) will harm plants. Rather, they have to expend enrgy to use it, which could otherwise be used for growth.

So in essence you're right, they don't need free ammonium. But if it's not there, they just make it themselves.
 
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