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Discussion Starter · #1 ·
You seem to be adding a lot of potassium with no water replacement. This is a problem.

Unlike NO3- and PO4-3; K+ is not chemically converted to other compounds and does not go away. It is always present either in the plants, animals or water.

My estimate is that you are adding 1.0ppm per day. If you add 1ppm per day over a year with no water replacement, your tank will be at 365 ppm!

Has anyone ever tested their water for K after a year on this system.
 

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Hi Ray,
I thought the same thing at first, to the point where I removed the K2SO4 from my mixture. However, I ended up with what I interpreted to be a K deficiency. I added the K2SO4 back to the mixture and the problem has not resurfaced. Your proposed scenario assumes no uptake by the plants which is not realistic. The K will end up being bound up in the biomass of the plants and you will end up removing it through trimming, etc. eventually. The plants are actually quite "hungry" for K and remove it from the water column. If I understand Edward's system correctly, the 1ppm per day that is in the PPS(-Pro?) recipe is actually shooting for enough for the plants to use for that day and not carry much, if any, over to the next day. Hope that helps,

TB
 

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Discussion Starter · #3 ·
K doesn't go away that easily

"The K will end up being bound up in the biomass of the plants and you will end up removing it through trimming, etc. eventually."

Well I thought about that.

As an estimate Let's assume that the level of potassium in a plant is the same as in human blood (I'm sure that plants have way less potassium than that but this will show you how much potassium you are putting in your aquarium).

Human blood is 159 mg./L (ppm) in K. To get rid of the K you put in a 10 gal aquarium you would have to throw away

365 mg./L * 10 gal * 3.75L/gal / 159 mg./L = 86L or about 190 pound of plant waste! That seems like an awful lot of plant waste from a 10 gal tank!

Has anyone actually checked the K levels in a 1 year old tank?

BTW, I have a Potassium test kit on order from LaMotte; so, I am going to check my K levels. I'd suggest that everyone do so as well.
 

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Unless you are having a problem and are searching for what might be causing it, testing for potassium might well be interesting, but isn't likely to improve how you fertilize. Most people use potassium for fertilizing aquatic tanks, either just from KNO3 or from that and K2SO4. People have not been reporting problems that have been identified as potassium caused. There may well be problems that people don't realize are caused by the potassium, but they can't be very significant ones or those, like me, who don't dose extra potassium would see a big difference from those who do dose extra potassium.

Still, it will be interesting to see what you measure with your test kit. And, it will be even more interesting to see how the potassium level changes with time with no water changes. I hope you will report your findings. There is still a lot that isn't widely known about planted tanks.
 

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Discussion Starter · #5 ·
You need to think about what you are doing

It is known that excess potassium my result in depletion of magnesium and calcium in some plants. It could be that what people are attributing to deficiency in magnesium is caused by excess potassium. It is interesting that the PPS requires the addition of additional Magnesium (something that is usually present in most hard water).

http://www.cartage.org.lb/en/themes...antHormones/EssentialPlant/EssentialPlant.htm

http://www.agcentral.com/imcdemo/07Potassium/07-02.htm

It seems to me (and I am not really an expert on plant fertilization) that what people are doing is putting some really potent chemicals into their aquariums in a programmed way without checking what they are doing (and maybe not even knowing what they are doing). The result can be some big imbalance that suddenly crashes! Something I think a number of people have experienced.

My feeling about this program is this:

You need to present data that shows what plant growth is like using the system vs. not using the system.

You need to present data that shows how the levels of each component you add to an aquarium change over time.

If you claim that it is safe for fish, you need to show how well fish survive on the plan vs. not on the plan.

OK I agree, this is not a lot of fun, but it is scientific, and this is a scientific board.
 

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Actually, very little real "science" is done here. We are more like pragmatists than scientists. There are just so many variables involved in a planted tank that doing real science with one is beyond most of our capabilities.

The Estimative Index fertilizing method uses even more of each nutrient than the PPS Pro method does, and a great many people have had good results with it. None of us could quantify those results, but we do notice that we can grow very nice gardens of aquatic plants, and the fish do very well living with those plants.

PPS Pro is a method that isn't quite the sledge hammer approach that EI is. Again, many people use it and grow very good aquatic plant gardens, with the fish living very well in the tank. So, we do have evidence that both methods are usable.

A few of the regulars here try to better match the fertilizers to the plants needs, and they too have good results and happy fish. So, my conclusion, as a pragmatist, is that you can do well with several different methods for fertilizing, meaning it isn't a critical element in having a nice aquatic garden.
 

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My estimate is that you are adding 1.0ppm per day. If you add 1ppm per day over a year with no water replacement, your tank will be at 365 ppm!
You are correct if you fertilize fish only tank. But why would one do such a thing? PPS fertilization program was design to feed plants, aquatic plants in 100% planted aquariums. If you can see substrate you don't have enough plants. Now plants will uptake K and use it.
 

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Discussion Starter · #8 ·
Now plants will uptake K and use it.
This is true but not the point! Plants take in PO4 and NO3 and chemically convet them into other compounds like proteins, lipids, ATP etc. PO4 and NO3 no longer exist when they become part of the plant. K is not converted into something else. Plants will only uptake K until it reaches the right electrolye concentration for the cell. After that point no more will be taken in and in fact the plant will have to start pumping K out.

I pointed out how much plant matter you would have to remove to get rid of all that excess K.

Now here is an interesting point! If your plants can concentrate all that K they could keep the water level of K low but this would be very unstable. The reason this is true is because unlike N and P, K is not part of the biomass and when the plant cell dies the K is immediately released into the water. The N and P have to be degraded by other organisms in the tank before they are released into the water.

Ok prove me wrong. Test your water for K and see what it is.
 

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Ok prove me wrong. Test your water for K and see what it is.
When do you expect to get your potassium test kit? I'm really very interested in seeing the results you get, because I have no idea whether you are correct or not. I'm going to post the question for Tom Barr on his forum just to see what his take on this is.
 

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Discussion Starter · #10 ·
They said there was a 15 – 20 day lead time on the K test kit.

I don’t think my results will be helpful as I am doing 20 – 30% water changes per week.

Here is a point to consider. If you add to your tank 1 ppm of K and NO3 per day for 5 days and then do 2 x 10% water changes for two days, the equilibrium concentration of K and NO3 will be between 10 – 20 ppm. That means you can never have an excess of these chemicals in your tank.

I think this is more like real biotypes than a continuous increase in chemicals. Real places with that type of environment are deserts or salt lakes like the Dead Sea or the Great Salt Lake. My feeling is that if you don’t do regular water changes, your tank will eventually crash. What you put in it doesn’t simply go away!
 

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I just finished reading an old "Barr Report" from 2005 on the subject of potassium and aquatic plants. The most relevant part I found is:

The amount of potassium removed through crop harvests is quite large. Typical concentration of potassium in healthy foliage range from 1 to 4% on a dry matter basis. It is reasonable to assume the same with aquatic plants given their rapid growth rates. In several crops, K removals are much larger than nitrogen and in some cases it is as high as 3 to 4 times that of nitrogen. It is used in larger amounts than any other element except N. Many plants have "luxury consumption", the plants take up more than is needed. K is not a part of any structural component of the plant as it is located in the cell sap as an inorganic salt.
Does this say more potassium is removed through pruning and pulling out plants than you calculated?
 

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If I have put 1 mg/L of K in the water per day, I have put 365 mg/L into the water in a year. A 10 gallon tank is 10x3.75=37.5 L of water. So, in a year I will have added 365mg/L x 37.5 L = 13690 mg of K, or 13.7 grams of K.

Per Tom Barr's paper on the subject, dry plant mass is at least 1% K, so to eliminate 13.7 grams of K would mean disposing of 13.7/.01=1370 grams of dry plant matter, or 1370/454=3 pounds of dry plant matter in a year, or less, if the percentage of K in those particular aquatic plants is more than 1%. A healthy aquarium will easily grow that much plant mass in a year, to be pruned away or pulled out and tossed. And, one wouldn't dose that much of any fertilizer unless the plants were growing well in response.

Did I miss a decimal place somewhere?
 

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Discussion Starter · #13 ·
Actually you and I agree!

3 pounds of "dry waste" is right; however, aquatic plants are about 98% water so if you include the water, you have to throw away:

3 x 100/2 = 150 pounds which is not that far from my estimate of 190 pounds.

Even going with the 4% dry weight that would mean throwing away about 38 pounds in a 10 gallon tank. If you have a 100 gal tank you would have to cart away 7 pounds of waste a week.

Of course all this is speculation. Someone needs to check the K levels over time to see what happens.

Here are some other points about these no removal plans:

What happens to the excess SO4 and Ca? Where do they go? Has anyone checked the change in conductivity of their water over time? This would be an indicator of a problem?

Everything you put in has to come out somehow. If not, you will have a desert!
 

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Well, the usual way here is to have people saying such a dose is absolutely not enough. Good to have you here. Ok, the dosed K amount was determined mostly on experiments done with a TDS tester and fully planted aquariums without water change for as long as three years or so. For example dosing more and more K while watching NO3 consumption to level up determines sufficient amount of K. All done on daily basis and maintaining consistent levels for test kit accuracy then calculated long term additions divided to an average per day dose. Additionally, watching TDS long term consistency as a proof of the right dosing levels and ratios.
 

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Discussion Starter · #15 ·
Ok, the dosed K amount was determined mostly on experiments done with a TDS tester and fully planted aquariums without water change for as long as three years or so. For example dosing more and more K while watching NO3 consumption to level up determines sufficient amount of K. All done on daily basis and maintaining consistent levels for test kit accuracy then calculated long term additions divided to an average per day dose. Additionally, watching TDS long term consistency as a proof of the right dosing levels and ratios.
Now that is really good information!

OK, I really don't have a problem with PO4 and NO3 the biology is that they will really go away over time. The problem is with the "spectator ions." The things you need to balance those acid radicals. K and NO3 are not used the same way in plants and checking for NO3 does not say that K is at the same level!

TDS is a clue that you are not overdosing with K but it is not convincing. If your water started at a TDS of 150 ppm and ended at the same value it could mean that there was 150 ppm of calcium and magnesium and now there is 150 ppm of K.

If you are not going to take any water out of your aquarium you have to check everything that you put in it including SO4, Cl, Na, etc. All of these can build up in a way that is independent of anything else you put in your tank.

OK, I think this plan is actually pretty good and I'm doing a modification of it in my own tank. The difference is that I am doing 20 - 30% water changes per week. By doing this I can add the same amount of nutrients that you recommend each week and be absolutely assured that it is impossible to have more than the recommended levels of nutrients in my tank.

I would be really interested to know the level of K, SO4, Na and Cl in a three year old tank with no water replacement.
 
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