PO4 addition required ??

[nbk3]

Ok , here goes , i'm trying to diagnose why my plants stop photosynthisizing a few days after water changes .

PUB water contains a decent amount of Chloride and Phosphates , which are both required by plants.

From the list of nutrients , The only nutrients i am not adding are Chloride , Phosphate .

Heres the scenario i observed :
After every water change (~30%) , and after i add in the fertilizers , the plants photosynthisize . But after a day or so , they stop .

Would it be wise to assume that the lacking ingredient would be Phosphate ??

Common sources of phosphate , i've heard , that its from fish food , and almost no excess food stays around since there are shrimps at work , there would supposedly no Phosphate elements that are avaliable for plants ??

Its a 2ft tank , planted , with a rather small bioload of a handful of shrimps , 10+ tetras . There is a layer of aquasoil below the gravel too .

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Dr malick supposedly sells KH2PO4 right ?

[bttay]

If you have fish in the tank, there will be supply of phosphates in your fish food. Assuming that your CO2 and lighting are enough, I think most likely is the amount of nitrate KNO3 that you should check. Next is iron if it is not inside your trace element recipe. Try test for these three elements to get a better idea of your water quality.

Dr. Mallick also sells KNO3 too btw.

Cheers,
Tay

[Perrush]

I think you can answer your queston yourself by measuring het PO4 levels by a testkit.
You should do the same NO3. If both are good (PO4 0.25 - 0.5 and NO3 5 - 10 mg/L) that take on the next macro element ... K.

Dose KNO3 (if you have a little margin with your NO3) or K2SO4. Aim for 5 to 20 mg/L K

Perrush ©

[nbk3]

NO3 , or nitrate , i believe that adding calcium nitrate will supplement it to an extent that it wun be lacking .

Thats how i came to a conclusion that Phosphate n Chloride were the missing links .

My view on the PO4 test kits are that they are incapable of measuring extremely low amounts , and even if they were present in very small amounts , it would be shown as Zero or zilch . The cost of a Test kit is slightly higher than a Pack of KH2PO4 from Mallick if i am corret , thus i would rather invest in it .

But afterall , i could be wrong .........

[bttay]

I think it is quite dangerous to dose phosphate without a test kit. If it happens that you overdose phosphate, there is a possibility of algae boom.

Although the PO4 test kit might not register low level but it can tell whether you are overdosing.

[bclee]

Actually, phosphate causing algae theory no longer hold.

I have had >20ppm of PO4 without algae problem. You can use the Tom Barr's estimative method.

I do "blind" PO4 doing too. I dose about 1ppm of PO4 each week.

BC

[juggler]

nbk3: PO4 is needed by plants too. In your tank, the level could be low if you don't frequent feed the fish. I dose 1.0ppm to 1.5ppm of PO4 every week for my high-lighting tanks.

[vinz]

I'm dosing PO4 blind too. 1ppm every half week. If I forget, I usually get algae on the glass a day or two after the missed dose.

[geoffrey]

Keeping PO4 at around 1ppm does not cause trouble. It causes problem only when other nutrients are lacking while the PO4 is at that level.

[nbk3]

Wow , thanks guys

I would say thay PO4 seems to be the most neglected nutrient of all The publicity it gets is one that associates it with Algae so i think majority of pple , who did not go deep enuff to see what is missing , would blindly follow the "PO4=Algae" myth

I just came back from crawford lane , got a 250gm for $4 , comes with a measuring spoon too [] hehe

Will try to let u guys know of the going ons

Cheers !

[theodore]

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On 8/11/2003 11:44:37 AM

Actually, phosphate causing algae theory no longer hold.

I have had >20ppm of PO4 without algae problem. You can use the Tom Barr's estimative method.

I do "blind" PO4 doing too. I dose about 1ppm of PO4 each week.

BC
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BC,

Isn't high PO4 level (>10ppm) lethal to fishes and shrimps?

[Perrush]

@ nbk3 :

How in the world can you dose something if you not know how much is in the water already ??

So it's not a question of 'investing' in a testkit or in a fertiliser. It's a quation of knowing what you're doing.

First step ... always ... is to know where you start from. So get some testkits and see where you're are. Even if they weren't that accurate, they'll give you an idea of what you have and what you haven't. Obtaining a analyse report of your tap water is also a good source of knowing what goes into your aqua.

AFTER you know what's in the water, you can start adding those missing. if you do it the other way round, one day you'll be wrong and you'll end up with a lot of mess.

[vinz]

Ok, better qualify my blind dosing...

Though I'm dosing blind now, I've determined, in the past, via test kits that my tank has low PO4. Usually the test kits read 1ppm or lower. Since I don't change anything that affects the PO4 supply in the tank (other then dosing) I'm comfortable that my "ambient" PO4 will pretty much remain that low. Observation over weeks have also confirmed that regular dosing of PO4 to my tanks keep the algae away. If I do add things like Jobe stick into the substrate, or do major uprooting, I would monitor the levels using the test kit for a few days.

My tank is actually high on nitrates. I dose trace and PO4 to keep up with that, high light and CO2. So similarly, in your tank you need to figure out what's happening and adjust accordingly.

[vinz]

Hmmm... NBK3, how often do you dose your trace elements? If you only dose after water change, of weekly, they might run out before the next dose.

[killua7]

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On 8/11/2003 2:22:47 AM

If you have fish in the tank, there will be supply of phosphates in your fish food. Assuming that your CO2 and lighting are enough, I think most likely is the amount of nitrate KNO3 that you should check. Next is iron if it is not inside your trace element recipe. Try test for these three elements to get a better idea of your water quality.

Cheers,
Tay
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While we're on the subject on testing, is there any LFS there would be willing to help test the aquarium water for you for free or a small price? This is because I find buying so many tests really not worth the money.

[geoffrey]

I see little point in getting the LFS to test your water. Afterall they will use those commercially available test kits. Why pay them when we can do it ourselves? However, it would be nice to have someone with laboratory graded equipments to do it but I think it will come with a hefty price.

[bclee]

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On 8/11/2003 2:55:03 PM

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On 8/11/2003 11:44:37 AM

Actually, phosphate causing algae theory no longer hold.

I have had >20ppm of PO4 without algae problem. You can use the Tom Barr's estimative method.

I do "blind" PO4 doing too. I dose about 1ppm of PO4 each week.

BC
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BC,

Isn't high PO4 level (>10ppm) lethal to fishes and shrimps?
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No. Livestock don't care too much about PO4 in the ppm level.

BC

[PeterGwee]

nbk3, with aquasoil in your tank, you can no longer use the pH/KH relationship to find your proper CO2 level which could well be what your tank is lacking now. K, PO4 and traces can be dosed over a wide range without much problems. CO2 and NO3 are the two biggest issue here..too much of either or too little will cause algae problems. NO3 is always best to be kept in the 5-10ppm range as too high NO3 will cause algae outbreaks as confirmed by Tom Barr after I wrote to him about it. Oh, so can high fish load too!

[nbk3]

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On 8/11/2003 4:04:03 PM

Hmmm... NBK3, how often do you dose your trace elements? If you only dose after water change, of weekly, they might run out before the next dose.

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i often dose it after water changes , and i'm starting to believe it aint enuff , although its just a small 2ft tank []

[nbk3]

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On 8/11/2003 4:51:33 PM

nbk3, with aquasoil in your tank, you can no longer use the pH/KH relationship to find your proper CO2 level which could well be what your tank is lacking now. K, PO4 and traces can be dosed over a wide range without much problems. CO2 and NO3 are the two biggest issue here..too much of either or too little will cause algae problems. NO3 is always best to be kept in the 5-10ppm range as too high NO3 will cause algae outbreaks as confirmed by Tom Barr after I wrote to him about it. Oh, so can high fish load too!
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thanks for the concern its the NO3 or nitrate i'm worried about , Thus i am considering about getting a NO3 test kit too . As the bacteria supposedly also produces NO3 Thru NO2 , i sometimes think whether there would be a need to add it thru the form of Calcium Nitrate .