Potassium K

[LookoutTrout]

I can find very little reference to urease in aquariums however many farming journals say urea makes a good fertiliser as urease in the soil quickly breaks it down, I am making an assumption that urease will also be found in aquariums.

Every answer I find is either too complicated or too simple.
This seems about the clearest and still doesn't help, is urease found in substrate?

Can I use Urea in my lawn hydroponic system?
It’s quite difficult to use urea fertilizer in a lawn hydroponic system because there’s no enzyme urease to catalyze the hydrolysis reaction.

Bacteria and fungi in the soil produce urease, a nickel-dependent enzyme. When Urea is added into moist soil, this enzyme starts a chemical reaction to break down the fertilizer to ammonium and carbonate.

However, in hydroponic systems, the urease enzyme is absent to start the chemical reaction of breaking down Urea in the presence of water. As a result, no nitrates are produced for grassroots intake.

[Vale!]

@LookoutTrout : just drawing your attention to the addendum I made to my previous post, in case you would otherwise miss it.

You would think that nature would find a way to deal with urea in water, wouldn't you? As you say, freshwater fish excrete ammonia via gills, and a very dilute urine via kidneys (marine fish seem to retain the urea they produce for an osmoregulatory process but I haven't grokked that!).

[Vale!]

... is urease found in substrate?

It would be helpful to our case if it were so - but I can't yet get a handle on that one. Lots of references to urease activity in riparian soil in forests, but they refer to the soil around a river, not under it!

New urease titbit : its action depends upon the nickel which it contains.

[LookoutTrout]

Further, it's seemingly becoming clear, via RNA analysis, that the role of nitrifying bacteria in aquariums has been grossly exaggerated and that in some/most established tanks the major agents are archaea (even when in tanks initially seeded with nitrifying bacteria)

I can't let that bit drift by, it contravenes almost every fish keeping guide.
I'd never heard of them before and still little the wiser but it appears they are the cause of fart smells so I'm interested.

[Vale!]

Doesn't it just, LT?!

Some time ago I banged on at excruciating length about this in Another Place ; nobody seemed that bothered, so I gave up. The only concession I made was to thenceforth refer to filter nitrifyers as "microblighters" rather than "bacteria". There is someone here who is onto it (he mentioned archaea in a post a few days ago) but it hasn't been generally a fruitful subject for discussion.

Apologies, but I feel a bit sniffy about starting all over again in this forum and wreaking further havoc to AP's thread! Tell you what, I'll PM you with a digest and a couple of citations ; if you feel moved to air the topic publicly you can report back to the forum in a new thread - maybe you'd have more success in eliciting interest than I did!

[black ghost]

It’s actually well accepted, now, scientifically, that bacteria are responsible for cycling, because they like the relatively higher ammonia and nitrite levels, but in an established filter, with trace levels, it’s mostly archaea.

(It’s also well known that a filter is a veritable war-zone, with different species chemically attacking their immediate neighbours, with constantly fluctuating population counts and increases and decreases of all the species involved).

Also I could be wrong but I think I’ve gleaned today that urea does break down on its own in water, very slowly, to CO2 and NH3/NH4...

[AngelPeace]

Getting back to the original debate (and by all means continue the other discussions)

So the reason for this thread was about out of control K. In summary we realised the reason my Nitrate test was not working was because Seachem supply Nitrogen in three forms, they being nitrate, ammonia, urea. The test only picks up one of those, Nitrate. Seachem website quote

However, if you test your nitrate immediately after dosing Flourish Nitrogen™, you will get a reading of only 0.5 mg/L because half of the nitrogen in Flourish Nitrogen™ is bound up as nitrate and the other half is bound up as urea.

So happy with that. Now then, whats really peeing me off is that I find the Nitrogen product also adds more potassium!! Nooooo. Come on guys, god they are obsessed with potassium. Its not used for binding the Nitrogen (is it?).

The Equilibrium adds a whopping 23% K (when we remineralise RO). Then we think, oooooh lets do the NPK method, give the plants Nitrogen and Phosphorus and the plants will eat the K. Well they wont if the Nitrogen product is also adding K.

I have emailed Seachem to ask them what they are playing at (:-)). I also realise it could just be my not understanding and happy to admit that if its the case.

Question 1: Why does Seachem ad soooo much K in Equilibium (VERY naughty)
Question 2: Why does Seachem feel the need to add K in to a purely Nitrogen dosing product (are they potassium junkies?)

Question 3 (Slight deviation but still relevant to the thread (the K issue): When I add PO4 (to balance the NPK) is shows immediately (well after 10 mins) but then after a couple of hours its all gone. Are the plants that hungry?

I have a 20 Gallon tank.
Added 5mls of PO4, took reading 4 hours later reading was <0.02 mg/l.
Added 10mls of PO4, took reading with a few mins, reading 0.2 mg/l (we are getting there I thought)
Added 10mls of PO4, took reading 90 minutes later, reading 0.4mg/l (yay that is my target)
Took reading the next day, its <0.02 mg/l.

Done this a few times, PO4 never stays in the tank, no matter how much I dose it goes to 0 within 24 hours. Is this good? Bad? Awful? A disaster? The best thing ever?

When I did this test, there was a very low source of NO3, since repeated it with NO3 dosing and doesnt seem to make much difference, and of course TONS of K (thanks Seachem). So regards NPK, heeeeelp. I need to understand this better, would love to hear from more experienced members.

Thank you so much

[AngelPeace]

@AngelPeace : Have a look at Seachem's knowledge base https://seachem.zendesk.com/hc/en-us/se ... -Nitrogen- concerning Seachem Nitrogen. I'm sure you'll find the first item in particular (the Article) of interest!

Ah! So there is a source of nitrogen (urea) that your test kit won't pick up. Almost half the weight of urea is nitrogen (I've just read). Anyway ...

In all probability, then, you've 'overdosed' your aquarium with nitrogen ; the jury's out on what constitutes an 'overdose' of nitrogen. You're not going to be able to tell exactly how much nitrogen is dissolved in your aquarium water because you don't have a test that will respond to a goodly proportion of it.

It seems a good plan to 'reset' your tank, if possible, via a series of partial water-changes (or one humungous water-change if your tank can bear it!) to get you back roughly to where you were.

Your future fertilisation regime, then, will require a choice :

You continue with, and have absolute faith in Seachem Nitrogen, dosing at its recommended rates, and somehow add sources of P and K. However because you can't measure the amount of nitrogen in a given dose, you're not going to be able to determine when you've arrived at your desired N:P:K! It is entirely possible to do it, but it would involve tortuous calculations (way too difficult for innumerate me!) and a balance that can weigh out perhaps very small amounts of liquid. On the 'plus' side, it contains urea which (as you've seen if you've followed my link above) is a highly desirable feature.

Or you could opt for a proprietary NPK preparation (such as https://www.pro-shrimp.co.uk/plant-fert ... 0909724087 - it's available in smaller amounts) which set NPK at generic ratios in line with their guess at what your planted tank is probably like.

Or you can go the Estimative Index (EI) route, which has the frequent reset of a tank built in to its regime. Again it doesn't typically contain a urea component, but EI's addition of nitrogen in the form of nitrate is a proven way of nitrogen-fertilising a planted tank, along with salts containing P&K and other elements. In theory you might still need a balance (depending on size of tank) but there may be a work-around for that. It would be possible, incidentally, to add urea [https://www.ebay.co.uk/itm/353311152979 ... BMmPTSmclg] - but then you're back to that calculation again. Mind you I suppose you'd only have to do it once. I wonder if there's an EI recipe somewhere that does use urea?


[Edit : to acknowledge Trouty's interposed post. I'm pretty sure that there has to be some kind of biological/chemical action, above simple dissolution, to get urea to turn into ammonia/um. I think aquautic plants do it intracellularly, if that's a word? And in soil it's probably bacteria using some kind of enzyme?].

Ive read all of the Seachem info on Nitrogen now, its a really good read thanks. Helped my knowledge. Yes thanks for links to the Nitrogen / Urea. I will consider the EI route. First I just want to see if I can learn the NPK dosing and get that right. So far I feel like I still have a lot to learn. See post above, some questions about NPK if you will. Thank you

[plankton]

Doesn't it just, LT?!

Some time ago I banged on at excruciating length about this in Another Place ; nobody seemed that bothered, so I gave up. The only concession I made was to thenceforth refer to filter nitrifyers as "microblighters" rather than "bacteria". There is someone here who is onto it (he mentioned archaea in a post a few days ago) but it hasn't been generally a fruitful subject for discussion.

Apologies, but I feel a bit sniffy about starting all over again in this forum and wreaking further havoc to AP's thread! Tell you what, I'll PM you with a digest and a couple of citations ; if you feel moved to air the topic publicly you can report back to the forum in a new thread - maybe you'd have more success in eliciting interest than I did!

This is why I call them "munchers".

[LookoutTrout]

To flip the original question slightly, why does it matter if potassium is high?