Roots in the water, maybe not.

[HTH]

For some time I have been espousing that for plants to remove nutrients from the water they require roots in the water. This is one of the cases where it may be nice to be wrong. Still one should obtain at least as good a result with roots in the water then with a potted plant.

This article (a good read) refutes that and at for at least some plants the preferred ammonia intake mechanism is not the roots.

Work with other plant species supports the above findings. Apparently, the seagrassAmphibolis antarctica can take up ammonium 5 to 38 faster by the leaves than the roots. And Myriophyllum spicatum planted in fertile sediment grew fine without any ammonium in the water. However, if ammonium was added to the water (0.1 mg/l N), plants took up more N from the water than the sediment.

This is interesting too.

The nitrogen cycle is often presented incorrectly to hobbyists as nitrifying bacteria converting ammonium to nitrates and then plants taking up nitrates. Actually, it consists of both plants and bacteria competing for ammonium. Only if plants are forced to, will they take up nitrates. Thus, nitrates may accumulate even in planted ponds and aquariums.

I read the above to mean that if one has enough plants there will be no or very low levels of nitrates.. To make this happen on has to have a veggie filter or a very heavily planted pond.

Aquatic plants, then, are much more than ornaments or aquascaping tools. They remove ammonia from the water. Furthermore, they remove it within hours (Fig 1, Table 2). When setting up a planted tank, there is no need to wait 8 weeks to prevent ‘new tank syndrome’. (Nitrifying bacteria require several weeks to establish themselves in new tanks and make biological filtration fully functional.) Thus, I have several times set up a new tank with plants and fish all on the same day.

Need to mention that in both ponds and aquariums the plant to fish ratio must be sufficient to handle the bio load.

I should mention that I have not seen studies for water lilies. It would be interesting to see such results. In either case I am staying with bare root if for not other reason then ease of maintenance.

[Much of this article was excerpted from Ecology of the Planted Aquarium by Diana Walstad. The book is readily available from Internet book sellers such as Amazon.com.]

 

[addy1]

Nice info!
I have no roots in water, all my plants are in pots, at the least the in pond ones. Now the bog, those roots are technically in water / gravel, since the water flows over them. I never have any readings when I test the water. Everything is zero.

 

[shakaho]

Most aquatic plants and algae use ammonia as their preferred nitrogen source. This results in that ammonia not being converted to nitrate, but unless you have enough of these plants/algae to use all of the ammonia, you will still get nitrates produced by your nitrifiers. That's why people can stuff their aquariums with underwater plants and still get high nitrates. Land plants and most marginals typically use nitrates. So if you have a planted bog filter, put land plants in the top of a barrel filter, tuck them in a trickle filter, or even set them in partially submerged pots in the pond, you aren't likely to have any nitrates.

 

[crsublette]

Interesting read. Howard, thanks for sharing it.

Diana Walstand. I thought this name sounded familiar. A friend referenced her to me a couple months ago and I actually have her new book, Ecology of the Planted Aquarium, which was just published this year. Also, on various aquatic plant tank forums, she is often in discussion along with Tomm Barr. Dr. Tom Barr also writes extensively about planted aquariums tanks and his forum is an extremely interesting read as well. Do aquatic plants prefer ammonium? There is more information Dr. Barr provides on the forum, but a premium must be paid to gain access to it. Dr. Barr has also conducted experiments regarding this subject and found only a miniscule improvement in plant growth, which is quite the opposite of what the articles says, when primarily relying on ammonia rather than nitrate to feed an "all planted" (no fish) aquarium.

Ammonium versus nitrate plant uptake is highly debated and, personally, I have not found the debated settled. The most recent discovery is that plants only use this ammonium for particular ammino acids and enzymes, which is produced in the plant and nitrates are used for high level functions and nitrates are reduced within the plant if sufficient ammonium is not present. Also, this ammonium will be in a constant battle with the growing bacteria colonies that form on the plant medium and plant's roots, which some have a symbiotic relationship with the plant in the exchange of sugars. I think much of it also comes down to the plant species. Supposedly, eichornia crassipes (a.k.a Water Hyacinth) consumes approximately 25% ammonium nitrogen and 75% nitrate nitrogen, in which the article states the opposite. Supposedly, as the article states, our typical algae has a nitrogen preference of ammonia rather than nitrate, because, since algae lacks the function to consume nitrate directly, the algae spends higher energy to use it's very inefficient nitrate reduction back into ammonia and is one variable that slows algae's growth. As an aside note, that is, it is a myth that high nitrates being one of the primary variables of algae blooms. Also, it is true that ammonia anion, due to the ion's negative charge, penetrates plant roots directly through some kind of biological osmosis and then, once insided the plant, the ammonia is very efficiently converted into the ammonium cation to be consumed by the plant; this is why particular plant medium, such as Laterite, significantly improves the consumption of ammonia for bacteria and for the plants.

Just one thing bugging me though... I would take to task the statement of "nitrifying bacteria requiring several weeks to establish in new tanks". I have seen sterilized tanks, without any bacteria product added other than the bacteria found on gravel and clay, have a mature bio-filter within 4~5 days under optimal conditions, but I guess the water in the planted aquarium tanks are not always created to have optimal conditions for nitrification bacteria colonization, that is in our context.

 

[HTH]

Great post Charles.