JamesC

One question that has never been explained to me is why do some manufacturer's use ammonium or urea based compounds in their products as a source of Nitrogen. On all forums I visit it is drummed into you how adding ammonium and urea to your planted tank will create algae mayhem and that potassium nitrate is the way to go. Do the manufacturers know something? I even tried replacing potassium nitrate with urea keeping the N amount the same for several weeks but didn't notice any difference in plant growth nor did I suffer any algae outbreaks.

James

jmhart

I've been involved in a few discussions about this, and the result was that most people that have used urea have had absolutely no negative results. Positive results are pretty subjective, but I believe *technically* nirtrogen from urea is more readily available to plants, so again, *technically*, urea is a better option.

Why we all use KNO3, I don't know except that we all operate off that conventional wisdom that urea or NH4 will cause an algae bloom.

This is, of course, in plant only tanks.

BryceM

It's a pretty controversial topic. There are plenty of people who add nitrogen in the form of either ammonium or ammonia. Actually, they're one and the same, since one is quickly converted to the the other at a ratio that depends on the pH of the water it's placed into.

As long as you keep concentrations quite low, you'll probably do just fine. Plants actually have an easier time assimilating ammonium than nitrate from a biochemical point of view. They do just fine converting nitrate to a usable form though and it's infinitely less toxic to the fish.

Zapins

Nitrogen also lingers in the aquarium a little longer than the other forms. Some plants have a little bit of a hard time absorbing nitrates vs. urea or ammonia.

It makes more sense to dose all three forms in very low levels. If you look at nearly all garden fertilizers they always have a combination of all three compounds for best results. Just make sure that the total N level doesn't exceed the needed N level if you decide to dose.

I believe freemann has been dosing ammonia for a long time now without problems.

AshK

According to what I've read by Dianne Walstad, the vast majority--if not all--truly aquatic plants uptake ammonium more readily as a nitrogen source than nitrates. Only marginal plants found around a water's edge use nitrates more readily.

http://www.aquabotanic.com/plants_an...filtration.htm

From what I've learned in botany classes, beneficial bacteria on plants convert nitrates quickly enough into ammonium for plant uptake. Because of this, I choose the "safer" route of using nitrates as a nitrogen source. I don't know if in actuality its "safer" or not, but after witnessing the damage of ammonia poisoning on fish I get a little uneasy around the A-words .

I look forward to reading more posts in this thread. Hopefully someone with first hand experience dosing ammonia/ammonium/urea will chime in and enlighten us.

wet

I've done this with Calcium Ammonium Nitrate (C.A.N.) but only induced greenwater, and I believe it to be my fault. At that point and with my amateur plant nerd understanding of chemistry I could not isolate NH4 uptake to plants, bacteria, or the greenwater, but N was gone all sorts of fast.

For those not aware but considering doing this experiment, remember to isolate N, by the way. For example, if I dropped about 10g of NO3 into my imaginary but awesome ginormous tank, I'd only need about 3g NH4 for the same dose of Nitrogen.

JamesC

I have decided to give dosing urea a go and see if there are any benefits. All plants currently grow great except for two. These are Alternanthera Reineckii 'lilacina' and Ludwigia Glandulosa which seem to grow with small and deformed leaves. I could of course always ditch these two plants but I like to persevere with them. I have tried different dosing stratergies from heavy EI through to a fairly lean dosing system that I currently use. Actually I found the heavier I dosed the worse the problem became with these two plants.

Been dosing urea for a few days and so far no problems. I'm adding 0.5ppm urea daily and have reduced the potassium nitrate so that the total nitrogen has remained the same. Potassium sulphate has been increased to compensate for the reduced potassium from the KNO3.

What I'm looking for is obviously an improvement in plant growth but also how nitrate levels change. If they drop then this would suggest that the plants are using the urea, but if they remain the same then this would suggest that the filter is getting to the urea first and converting it to nitrate. Because urea has a very high N content I'm now dosing about a third of the potassium nitrate as I was before, which is quite a difference.

I'll update this thread on any progress.
James

Mr_docfish

I have been dosing NH4NO3 for some time now... 1.5g per 1000l daily. I do have a 9W UV unit running 24/7 as I have 450Watts of MH lighting the tank with CO2, so I am asking for green water if I add NH4.
down side is the leftover H+ that will slowly drop the pH.... I do a trade off with adding Ca(OH)2 every week. I test the water weekly, particularly the pH after allowing it to stand for 24hours to let off the dissolved CO2. I also add KHPO4 for the PO4 levels, so the amount of Ca(OH)2 will vary according to the amount of NH4NO3 and KHPO4 added to the tank on top of the normal organic acids being produced.

JamesC

It's been two weeks now since I started dosing urea and I have noticed a dramatic change in my Alternathera Reinekii and Ludwigia Glandulosa. Both are now producing much larger and non-crinkled leaves compared to before, which I must admit has surprised me. All other plants are growing exactly the same as before except maybe the Rotala Macrandra which seems to look fuller and healthier.

This better growth could be due to the added urea but it could also could be due to the lower levels of nitrate that I've been dosing. Next step is to increase nitrate levels again and see how the plants react.

There have been no noticeable effects to fish or shrimp and also no algae problems.

James

Coralite

Aquatic plants have a negatively charged surface. Ammonium is positively charged so it takes less energy for plants to uptake NH4 than NO3 which is negatively charged. If I was just growing plants I would add ammonia as needed but seeing as I like to keep the nitrogen availability high, if I dosed ammonia at the same concentration as NO3 my fish would die.

JamesC, I would like to hear/see more about the change in the leaf appearance you've noticed by dosing ammonia.