How to negate/slow down the breakdown of urea into ammonia

[JoelB]

I have dosed urea for nitrogen without realising that it would remain partially stable until certain conditions are met. I can measure 2ppm ammonia, then do a 50% water change and see 2ppm again shortly after.

What can I do (or not do) to slow down the process or neutralise the urea?

[MTiffany]

Maybe a little late to the party here, but after doing some poking around on the web, IMHO I don't think there is anything that you can do slow down the conversion of urea (http://en.wikipedia.org/wiki/Urea) into ammonia.

Urea is broken down by bacteria using an enzyme called urease (http://en.wikipedia.org/wiki/Urease). For each molecule or urea, two molecules of ammonia are produced:

(NH2)2CO {urea} + H20 {water} + urease {enzyme} --> 2(NH3) {ammonia} + CO2 {carbon dioxide}

Seeing as how these urea-eating bacteria are ubiquitous in the environment (as just another step in the Great Cycle Of Nitrogen) they are going to be in the tank and their population will probably grow as quickly as the concentration of urea in the tank water will allow. That's why I don't think there's much you can do (short of a 100% water change). Nobody ever wins a battle with Mother Nature.

Out of curiosity, how long did it take to convert all the urea in the tank?

[JoelB]

I wrote in another thread that I dosed some tap water with urea and took a measurement, then based on that I put a medicine cup of urea into 55G. It took a week to see signs of stability during which time the ammonia generally stayed at 6ppm or so and I did two 50%, a 75% and a 90% water change. It took another week to return to normal. The whole time I was keeping on top of the ammonia with prime.

I've since found out that I only need a single 1/4" grain of urea to raise the ammonia to around 1 for a day and a half. If I add it every day or two and wait a few days for the cycle to catch up, then there is no measureable amount of ammonia with the additions.

Thanks for the explaination. I used to think it was chemical, not biological.

[Canuck]

Why don't you just dose Nitrates? Algae loves ammonia even more than plants especially fluctuating levels.

[JoelB]

I'd much rather dose potassium nitrate rather than urea and potassium sulphate, it's just not the right way to do it...but potassium nitrate is a little hard to come by these days.

[Canuck]

http://www.bestaquariumregulator.com/ferts.html

http://www.aquariumfertilizer.com/index.asp?Option1=new

Or the pharmacist at your local drug store would probably order it in for you.

[plantbrain]

I have dosed urea for nitrogen without realising that it would remain partially stable until certain conditions are met. I can measure 2ppm ammonia, then do a 50% water change and see 2ppm again shortly after.

What can I do (or not do) to slow down the process or neutralise the urea?

Osmocoat time release ferts have been around for decades..........but it does not slow the process down, just the leaching rates.

I think more than 0.8ppm of NH4 per day is way too much for most systems.
If you want to dose NH4, just use MS or ADA AS and get it from the sediments.

Or a decent fish load, then add KNO3 for the rest and to reduce the demand on the sediment and fish loading so those sources last longer.
Stump remover, various mail order places all over the world, in Europe, the UK, USA certainly are available. Most other places have few restrictions on smaller amounts, see any agriculture supply place, 50lbs runs about 30-50$ USA.

Regards,
Tom Barr

[JoelB]

I did the grain test within a few days of the tank returning to normal so there may have been elevated urease levels and beneficial bacteria levels and I'd hardly call it controlled lab conditions. Anyway if I wanted to dose less, I woudn't want to split grains and I wouldn't know how many days I could skip between additions while expecting the filter to remain cycled up to dealing with the dose.

My fish load is a little low right now but some of my fish are young and the tank will be full when they grow. For the plants I add some GH to the change water and some trace with iron from a bottle. I also try to keep on top of the phosphorous and nitrogen ratio...which is what got me into this mess.

I also have an occasional hole in the leaves/leaf curling issue that I guess is a potassium shortage. My supply of potassium sulphate is impure.


@Canuck, I'm on to an online supplier, thanks for the suggestions.