How much Potassium Phosphate (KH2PO4) for 300 litre heavy planted tank?

[ceg4048]

My problem is that if a beginner reads that there are no negative effect of any of these things and test is a bad thing just use spoons no matter how your plants grows will lead to more problems.

Viktor, the answer to this is to understand cause and effect. We know from Barr's testing that EI levels of nutrient salts have no effect on the health of fauna, although we know that the salts quickly drive up the TDS. So if we know that it's OK, and if we know that nutrients don't cause algae, then why program you customers to get hooked on test kits that tell lies?

Cheers

 

[viktorlantos]

Adding another tweak to the PO4 madness. Meanwhile we're talking about adding in more and more PO4.

Other ferts like ADA has 0 PO4. Nitrate is at 5ppm or under.
It is not about brand now, but a different side of the story.

We all can agree that they are using high energy tanks mainly. Lots of CO2 high light. Yes we can argue that Solars power are not that strong (seen this many times on the board 🙂 ), but hey Grand Solars are also in used anyway. Most of us use less light for less hours then they do.

The reason why i am pulling this up not because of the brand, but another way which also works quite well.

So this is why i am telling to my clients if they do not see any difference on their plants on a short therm with additional PO4 then leave it.

 

[dw1305]

Hi all,

PO4 test kit silliness is new to me i know many tests fail or inaccurate or works differently in soft or hard water, but it was new to me

Most anions are quite problematic to measure. Orthophosphate measurement is more repeatable than nitrate (NO3-), but you need the right reagents to get reasonably repeatable values.

In water you need a measure of the PO4--- ion in solution, but particularly in hard water you get a certain amount of suspended insoluble calcium phosphate as well. This may become plant available in the substrate (via REDOX reactions), but won't be available in the water column.

Assuming we are just interested in PO4--- ions, you would use a colorimetric method, where a reagent reacts with orthophosphate and the resulting blue colour is directly proportional to the amount of orthophosphate in the water. For accurate measurement you would need a standard curve from known PO4--- samples and a spectrophotometer set to 740nm, but you could get an approximation from a colour chart.

The real problem is the reagent (which contains sulphuric acid, potassium antimony tartrate, ammonium molybdate, and ascorbic acid). Potassium antimony tatrate is a cardiac poison and powerful emetic.

cheers Darrel

 

[viktorlantos]

Hi all, Most anions are quite problematic to measure. Orthophosphate measurement is more repeatable than nitrate (NO3-), but you need the right reagents to get reasonably repeatable values.

In water you need a measure of the PO4--- ion in solution, but particularly in hard water you get a certain amount of suspended insoluble calcium phosphate as well. This may become plant available in the substrate (via REDOX reactions), but won't be available in the water column.

Assuming we are just interested in PO4--- ions, you would use a colorimetric method, where a reagent reacts with orthophosphate and the resulting blue colour is directly proportional to the amount of orthophosphate in the water. For accurate measurement you would need a standard curve from known PO4--- samples and a spectrophotometer set to 740nm, but you could get an approximation from a colour chart.

The real problem is the reagent (which contains sulphuric acid, potassium antimony tartrate, ammonium molybdate, and ascorbic acid). Potassium antimony tatrate is a cardiac poison and powerful emetic.

cheers Darrel

So good reagent and soft water?
BTW we only use soft water in our tanks around 100ppm TDS.

 

[Edvet]

I realy would like a sticky with all these arguments (why certain tests won't work) so we could point people to them, or also a sticky wich has links to the most often used statements here ( like the PAR graphic, the light colour stories, the pH profile etc etc).
Would a post with a lot of reserved answers work so the statements can be copied/pasted in it?

 

[viktorlantos]

Viktor, the answer to this is to understand cause and effect. We know from Barr's testing that EI levels of nutrient salts have no effect on the health of fauna, although we know that the salts quickly drive up the TDS. So if we know that it's OK, and if we know that nutrients don't cause algae, then why program you customers to get hooked on test kits that tell lies?

Cheers

My point was that there could be different kind of issues too than algae. We frequently talks about how to avoid algae and everything is aligned to that.

I mentioned shrimp death and plant leaf loose on a specific specie, but based on your example my situation maybe was special.

 

[Marcel G]

Zak, 7.66 grams of KH2PO4 mixed in 500ml water and dosed 150 ml per week (3x50) means you are adding 5.35 ppm PO4 each week into your 300L tank.
I agree with what Victor said. If you have some clay substrate it can absorb really high amounts of phosphates. Once I added nearly 30 ppm PO4 into my tank in one dose, and the second day I measured only 5 ppm, and the third day there was just zero PO4 in water. Most aquatic plants grow exceedingly well at a concentration as low as 0.3 to 0.5 ppm PO4. But there are some plants which are able to store phosphates more effectively then others, so they can absorb most PO4 from water and store it in their tissue "for a rainy day". This you need to account for.

For sure you can add much more PO4 into your tank (even after your substrate saturates with it). It sounds great and interestingly when someone says that you can dose 10 ppm PO4 or whatever amount you desire, but the point is: What do you gain by it? Do you really want your plants to grow like mad, so that you have to trim them each week? Do you really want to adjust your layout each week? I give you one month ... then you give up. If you don't sale plants for living, then you can have a nice planted tank with 0.5 ppm PO4 with quite a reasonably decent growth. There is no need to pump 3 ppm (or even more) PO4 ... especially if you use ADA Aqua Soil which is nutrient rich. The EI method is really good if you want to sell plants, otherwise it's annoying. You spare some time on testing water parameters, but you spend much more time with plant trimming and replanting.

 

[viktorlantos]

I realy would like a sticky with all these arguments (why certain tests won't work) so we could point people to them, or also a sticky wich has links to the most often used statements here ( like the PAR graphic, the light colour stories, the pH profile etc etc).
Would a post with a lot of reserved answers work so the statements can be copied/pasted in it?

Would be really useful.
Especially as we use soft and hard waters. When to use this or that. When tests will not work.
Here science could help for us to see the light 🙂

 

[viktorlantos]

The EI method is really good if you want to sell plants, otherwise it's annoying

I see why you say it honestly 🙂
But the loveliness of healthy plants are priceless 🙂
Many times helps to not think about deficiencies.

 

[ceg4048]

For sure you can add much more PO4 into your tank (even after your substrate saturates with it). It sounds great and interestingly when someone says that you can dose 10 ppm PO4 or whatever amount you desire, but the point is: What do you gain by it?

What you gain is healthy plants free of algae caused by poor flow or PO4 deficiency.
My point is NOT to encourage people to add 10ppm of PO4. I think you have misinterpreted this. My point is that you CAN do it without reservation and that adding PO4 does not harm fish or cause algae. There is a generation of hobbyists out there that think PO4 is bad. My goal is to show that the mentality is wrong. So if I can add 10ppm of PO4 to a tank and have my only problem be massive pruning requirements, why is that a bad thing? If I need to increase growth rates for ANY purpose, not just selling, why is it bad?

EI does not care WHY you want healthy plants. That's your business. EI merely states that you can improve the health of you plants without fear of algae or negative effects on fauna. If you want to reduce the growth rates then EI allows for that as well. I don't see why this is an issue.

Cheers,

 

[dw1305]

Hi all,
Others will disagree, but I'd be surprised if any-one who adds PO4 regularly has plants which are phosphorus deficient. Even though phosphorus is one of the macro-nutrients, plants need only about 1/10 as much P as they do nitrogen (N) or potassium (K).

If you have hard water you won't ever have much PO4--- in solution, however much you add, because it will precipitate out as insoluble calcium phosphate complexes.

So good reagent and soft water. BTW we only use soft water in our tanks around 100ppm TDS.

You probably will get a fairly accurate measurement, mainly because there are many other ions to interfere with the process. The only proviso would be if you had high iron (Fe+++) ion levels, which again would lead to insoluble compounds being produced.

There is some discussion of test kits (including phosphorus) here: <"Accuracy of test kits..">.

cheers Darrel

 

[Jose]

Yes plant growth can be controlled via low PO4 as well as low lights. But if you keep phosphates too low then chance of problems is higher.
I suppose if you want a slow growing high lit tank then you have to have low phosphates but this is not a very common type of tank.
Also when people talk about ADA tanks they should consider the soil as well.

 

[viktorlantos]

ADA Amazonia soil does not supply po4. Other ADA soils does not supply anything like malaya and africana. But mainly amazonia used.

Yup high light slower growth less maintenance (on decors too). But more closer look on overall health and immediate action on issues vs the ei way of turbocharged plants no defficiency more trimming more maintenance more po4 because of the green glass and decors 😉

I use both method each has advantages and disadvantages

 

[Jose]

ADA Amazonia soil does not supply po4.

I believe it does. Its origin is some form of organic soil. Someone can clarify otherwise.

http://www.ukaps.org/forum/threads/the-science-behind-ada-additives.16579/

 

[Marcel G]

I'd be surprised if any-one who adds PO4 regularly has plants which are phosphorus deficient. Even though phosphorus is one of the macro-nutrients, plants need only about 1/10 as much P as they do nitrogen (N) or potassium (K).

Recently I do some tests with nutrient uptake in my two tanks.
In one of my tanks I use 100-400 µmol PAR (high light), ~35 ppm CO2, and I have no substrate, not fish, nor any filter media in this tank to eliminate its influence on nutrient production and nutrient uptake by plants. Although I was adding about 1 ppm PO4 into this tank, my Ludwigia palustris was suffering a severe P deficiency (it took me some time to figure it out, but finally I found it is P deficiency). But still I don't think my plants are able to consume this amount of PO4 in this tank, as I have a similar tank with nearly the same conditions, and according to my tests the plants there consume only about 0.4 ppm PO4 per week. The problem in my first tank can be the PO4 precipitation (as Darrel pointed out). If I had a substrate there, the PO4 precipitates could be mineralized and used up by plants finally. But this way they have no chance to use it. So I think that even in high light, densely planted tank with many fast growing plants (like the one I have) we don't need more then 0.5 ppm PO4 per week (in case we have no fish, no fish food, and no substrate). In case we have some fish, and especially when we have some nutrient-rich substrate, we may need even less (or none at all).

I did ADA Aqua Soil Amazonia lab analysis (8/2014), and I showed up that the substrate contain <2 ppm P/kg (i.e. <6 ppm PO4/kg). P in this case mean accesible/available P (the one plants can directly use). This level is very low according to the lab.

 

[Marcel G]

BTW Clive, I have a plant biomass yield of 1.6 g/dm2 (fresh weight) in my tank → 100-400 µmol PAR, ~35 ppm CO2 (maybe even more), and 40-50 ppm NO3, 3 ppm PO4, 0.5 ppm Fe. So even if the P content in dry matter was 0.5% (which is about 2-times more then the average values in most aquatic plants), the real PO4 consumption in this tank would be 0.6 ppm PO4 per week (despite the fact that I'm adding 3 ppm PO4 into it each week).

Please, can you tell me what is your biomass yield in your tank where you add 10 ppm PO4 per week? I would like to calculate how much P your plants can really utilize from this huge amount.

 

[parotet]

In the reported case, adding more PO4 exposed the fact that the CO2 was low. Adding more of any nutrient drives an upstream demand of other nutrients.

This has been my battle over the last year and what IMO is not enough explained to newbies. EI is supposed to be an "easy method" (no need testing, no need accuracy when dosing, etc.) and I agree with this, BUT most of us end up adding weekly PO4 levels of 2-3 ppm (the "standard recipe" that can be read everywhere. Yes, I know, it is a flexible regime, but we all use this recipe as a reference). As mentioned by Clive, adding more PO4 (I would say, adding these levels of PO4) expose the fact that CO2 is low. And we all know that having high, good and consistent CO2 levels is one of the most difficult things in planted tanks, especially for newbies. Therefore it seems to me that this "EI easy approach" can really push lots of people to have CO2 problems... Yes, PO4 levels of 2-3 ppm may not be the direct cause of having BBA (there are thousand of tanks to show this), but it drives easily to poor CO2 scenarios and finally to BBA (there are also thousand of tanks to show this).

In my tank (medium light) and probably due to my low CO2 skills (and very hard tap water), I have been much more succesful following a lean EI approach, which at the end is a PPS-Pro dosing regime, what Tropica and Seachem recommends with their comercial ferts regime, and probably what is achieved in an ADA tank when combining ADA ferts and AquaSoil. With medium light I can be flexible with PO4 (have it higher or lower), with high light and high PO4 I got BBA on lower and old leaves....

Another argument which is continiously repeated in this fórum and I don't agree with is that ADA setups are low light... Come on, of course there are some (especially display tanks to ease maintenance), but have a look to the PAR measurements done with the AquaSky series (not to mention for example AquaSky 602). This is really photon bombing! And these tanks do work with leaner dosings and much less accurate distribution (let me make a little joke 🙂 Can you see a spraybar in a planted tank? This is for sure an EI doser...) (although I have to admit that most of this successful superlight ADA tanks work with huge filters that even exceed the 10x rule of thumb)

Jordi

 

[Jose]

I agree with parotet. I dont think EI is an easy method mainly because most people have high light and probably dont know it. But in the end this is the users fault. People are told to put CO2 higher but maybe they should just lower the light.

 

[Marcel G]

That's a very good point, Jordi => ADA Aquasky 601 (= 150 µmol PAR at the substrate level) combined with ADA lean ferts + ADA substrate (rich in N+Fe only → 4 g/kg N and 30 g/kg Fe, other nutrients are there in a very low amounts). How is this working without 3 ppm PO4? Maybe our plants really don't need as much P as EI people think. So even though we CAN add 10 ppm PO4 into our tanks, maybe our plants are ABLE to consume just 0.1 to 0.5 ppm per week. That would explain why the plants can grow well even with leaner dosing regimes. And maybe our plants don't need as perfect CO2 as many thinks. Most ADA tanks use simple diffusers (which are [together with lily pipes] often blamed for bad CO2 dissolving and bad CO2 distribution), and still have excellent plants, and no visible algae. I myself know a few stunning planted tanks with 150 µmol PAR at the substrate, no PO4 in water column (except what fish produce), and with only 15 ppm CO2 (lily pipe + diffuser). Why people don't want to know how much PO4 (or other nutrients) their plants really need, and instead they just pump tons of PO4 into their tanks? This seems like ignorance to me. We play on being good horticulturalists, but we don't even know our real plants' needs. We grow plants but don't even know how much CO2 or other nutrients are needed. Tell me what is the compensation point, half-saturation point or saturation point of photosythesis for NO3, PO4, K or Fe (i.e. how much of these nutrients is needed for plants to begin to grow, to grow at 50% of their maximum, and to grow at their maximum growth rate)! Even after 35 years (or so) of using CO2 cylinders no one knows!!! And no one seems to bother.

First of all, we should know what our plants need! Then (and only then) we can be sure we supply them enough or not enough "food". To add 10 ppm PO4 into any tank is just foolish IMO, because it just manifests the person doesn't know anything about his plants' real demands. For example, if I know that my plants are able to consume 0.5 ppm PO4 at the most (under given setup), and that they need minimally 0.1 ppm to grow well and don't suffer any deficiencies, then it's more then obvious what are unlimiting values and what would lead to deficiencies (no need to exaggerate and use 10 ppm only to look interesting).

 

[Jose]

So Ardjuna if you can put a link to your experiments then we can have more light on the matter. There are a few factors we still dont know. If plants only use up 0.5 ppm of PO4 then we shall investigate, but for this there has to be some proof. Even so one thing is the comsumption and another different one is the levels at which plants start doing better.

Ada tanks have easy explanations. They have just the light needed to pearl. They have a substrate which is leaching nutrients continiously. Co2 as bubbles in a tank have been shown to be very effective.