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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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I thought about this a lot over last summer. I decided to take pretty much every filter off my 75G plant tank. The only filters I have are basically a sponge over my overflow to prevent fish from going down into the sump, and a drip of water per second, flowing over bio balls. This is just in case.

So I guess yes you can run filterless, just ensure you have healthy plants, cause if they stop growing, they won't be removing anything, and if they start dieing, they will be contributing to the bioload of the tank.
 

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I also have thought about this from time to time. I get the feeling that maybe it paases throught everyones mind occasionally. The only problem I can see wiht it is the lack of flow in the tank which seems like it would lead to algae problems, no matter how healthy the plants. Dead spots in the water colum are something you really want to avoid. I guess you could just use a power head though, or more, depending on the size of your tank. Do you do anything like this Justin? As far as the NO3 NH4 isue goes, the plants would have the fill of NH4 since it forms first. ANy that was not consumed and converted to NO3 would then be taken in by hte plants. That assumes a healthy, balanced tank. That is the reason we usually need to dose NO3. Thats just the way it seems to me. I am sure it is probably more complicated than that but..........

So, I wonder how many out there go filterless?
 

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You should check out Diana Walstad's book "Ecology of the Planted Aquarium." It can answer all of these questions for you. :)
 

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Per D. Walstad NH3 (ammonia) is toxic to plants. It doesn't have a charge and tends to permeate cell walls unrestricted. NH4+ (ammonium), which is normally a terrestrial plant fertilizer, is not. I think the problem is that they both exist simultaneously and their respective amounts vary with pH. A pH change can convert NH4+ to NH3 and kill fish and plants. Plants do prefer NH4+ over NO3.

I keep those Ehiem pebbles and ceramic cylinders in my filters for biological filtration, as I feel it can't hurt. I think it is dangerous to try to make NH4+ available to plants... too risky. Also adding NH4+ to a tank is taboo.

Steve Pituch
 

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Graham,

Plants need both NH4+ and NO3- for optimum growth. It can never hurt to have some sort of filtration in your tank other than your plants. One can never tell when something might happen that causes the plants to not use up the materials as quickly as they used to. The buffer provided by filters is very handy. They're also good for removing particles from the water. :)

On the topic of NH4+ and NO3- once a tank is established the amounts of NH4+ being put off into the aquarium are negligible compared with the amount of NO3 available. Also, since NH4+ has a positive charge it will bond with the negatively charged particles in the substrate and will be either sequestered there or taken up by the plants' roots. NO3- on the other hand will be rebuffed by the substrate and will stay in the water colum for the plants to take up through their foliage.

To summarize: NH4+ is more readily broken down by plants, but it exists in such small quantities compared to NO3 in an aquarium that there must be both. Having a filter will both a) provide water movement and physical particle removal and b) provide a source of NO3- as well as a backup in case something happens to your plants.

Best,
Phil
 

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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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Everything is biomedia. Your crushed dolomite would act as biomedia. A biofilm forms on everything in the filter.....and the tank.

If you need a little more mechanical filtration use some aquarium gravel in one of the baskets with maybe a little fluff at the bottom of the basket, but the gravel will also function as biomedia.

Steve Pituch
 

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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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Yes, I agree. That's why I often use gravel as a media. Its got surface area and acts as a filter media.

I think of the filter media and all of its bacteria as an extra amount of biofiltration. When you clean a filter the shock to the bacteria has got to be severe, putting the bacterial activity out of commission for a while. The biofilms in the tank, substrate, and plants are plenty to keep things going in the tank as if nothing happened in the filter. That's why when its time for me to clean a filter I go all out, often bleaching all the components. If I turn a filter off for less than 24 hours I don't worry about it hurting the tank when I turn it back on. But if its been off more than a week, its time to tear it apart and do a thorough cleaning (by that time everything is anerobic or stinky).

Steve Pituch
 

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I run my new 20gallon with just a powerhead. And i do wish i have a filter on the thing, i'll have to wait for my summer job. I'll say this, i have miracle grow potting soil under Eco-Complete. The miracle grow was boiled however. Anyhow it takes the plants forever to grow roots down into the miracle grow. So until then i have to add KNO3 and traces to get the plants to grow big leaves, otherwise the leaves are maybe 1/8th the size they are in my other tanks. I still cannot get them 1/2 as big, but its only been 2 weeks. The tank is coevered in brown sludge now. And i planted the tank medium to light. I think if you were to run filterless things are far more touchy. You must plants very very dense to start off filterless and you must wait twice as long to add fish, or in my case almost 7 times because i usually add fish the 2-3rd day. A lot of biomedia is maybe not important. but better save than sorry. If ammonium was so good for plants then how do people like myself and other have any success growing plants (I have to go 50ppm of co2 to get my ph below neutral). I think maybe my plants would have larger leaves if i had acidic water, i think Tom barr said PH has more affect than we give it credit for, But plants dont need the NH4. Its the luck of the draw i guess.
 

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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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I've read the post before. I am no scientist but from what i understand ammonium is like sugar and nitrate would be like a complex carbohydrate.
 

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NO3 is always converted to NH4 in plant cells. Some plants have opreferences of NO3 over NH4, generally most prefer one over the other but does reflect in practical terms in a tank? No, not much.
In isolated test, yes, you can show this, but at those levels of NH4, it's toxic and will cause algal blooms.

In order to meet the N needs of plants in CO2 enriched tanks, adding NO3 is needed.

If you want to reply on a heavy fish load for this, it is VERY WISE to have a good filteration system.

Ask your self this: which would you rather have, have to add a bit more NO3 and have some bacterial back up .....or algae?

A good filter, not an excessive one is good for most planted tanks, if you have way too much fish, having a large filter will help.

If you have few fish, sure, you can get away without a filter. But most use one for a back up. Plants will get the NH4 if they have good CO2, K, PO4, Traces etc, if you louse those up etc, then the uptake NH4 will decline and with no filter back up, what do you get?

You can try it and see for yourself.

Ultimately though...............all the NH4 and NO3 is going to be used by the plants.
So even if the bacteria do oxidize the NH4, it'll still be removed by the plants, so don't worry about it and set things up for redundancy in case something does go wrong(and it will at some point).

Regards,
Tom Barr
 
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