Po4 Plant Uptake?

[blahblah]

I've been dosing Seachem phosphorus into my tank - I've only been adding ferts for 1.5 weeks, and the tank is only 3.5 weeks old - 2 days ago the phosphorus test was 0.5ppm. I wanted to get the levels a little higher, so dosed 50% more than normal on the same day as I did the test.

Today I tested again for PO4 today, same result, 0.5ppm.

I am guessing either the uptake for phosphorus is reasonably signifacant, or my test kit is not sensitive enough (aka crap!). I am using Hagen PO4 test kit.

I then added 10 drops of Seachem Phosphorus to the water sample post test, shook the test tube, and no difference! Is that a reasonable test for the sensitivity of the test kit?

What does anyone think about this? Maybe this is all normal, but I'm a definite newbie , and would appreciate some input from the people who know

nitrate 40ppm btw

Thanks

 

[SuperColey1]

Standard test kits are incredibly inaccurate and I don't really understand why anyone uses them!!!

I for sure don't. My eyes watching fish and plants tell me if the parameters are wrong.

.5ppm (if it were true) should be OK as it means that there is some P in the water. If the P gets too low you will see green spots developing on leaves (not string just like the green you get on the glass.)

If you don't have green spots on leaves or glass and the plants are growing healthily then stop testing.

Andy

 

[blahblah]

Standard test kits are incredibly inaccurate and I don't really understand why anyone uses them!!!

I for sure don't. My eyes watching fish and plants tell me if the parameters are wrong.

.5ppm (if it were true) should be OK as it means that there is some P in the water. If the P gets too low you will see green spots developing on leaves (not string just like the green you get on the glass.)

If you don't have green spots on leaves or glass and the plants are growing healthily then stop testing.

Andy

Thanks Andy. It seems the test kit is ok actually, or at least my experiment of adding 10 drops did result in a change of colour within the tube - only it took some hours to react! A guy on plantedtank.net has done quite exstensive calibration tests on the nutrafin/hagen test kit, with good results, which helped rebuild some confidence with this testing lark.

Hopefully with experience I will get to the point where I can 'read' the plants sufficiently and understand what's going on without testing quite so much. Meanwhile I'm still testing fairly regurlarly to try to assess uptake as best as poss.

 

[plantbrain]

Standard test kits are incredibly inaccurate and I don't really understand why anyone uses them!!!

I for sure don't. My eyes watching fish and plants tell me if the parameters are wrong.

.5ppm (if it were true) should be OK as it means that there is some P in the water. If the P gets too low you will see green spots developing on leaves (not string just like the green you get on the glass.)

If you don't have green spots on leaves or glass and the plants are growing healthily then stop testing.

Andy

Thanks Andy. It seems the test kit is ok actually, or at least my experiment of adding 10 drops did result in a change of colour within the tube - only it took some hours to react! A guy on plantedtank.net has done quite exstensive calibration tests on the nutrafin/hagen test kit, with good results, which helped rebuild some confidence with this testing lark.

Hopefully with experience I will get to the point where I can 'read' the plants sufficiently and understand what's going on without testing quite so much. Meanwhile I'm still testing fairly regurlarly to try to assess uptake as best as poss.

No no no!

The person who did that test had a sample of 1!
Statistics wise, you cannot say anything about that test, other that particular kit that he had was within the parameters.

You must test and calibrate YOUR TEST kit, do not reply on a sample of 1!
Ever.........
You cannot come to any conclusion with that kind of smaple about general inferences to all Hagen Test kits.
There is a lot of variation in any sample.

So either calibrate the test kit, or just assume it's wrong/you simply do not really know.
Those are the only choices.

Unless you run a sample of say 20 to 30 Hagen PO4 test kits from around the world, some sit on the shelf for 3 years, some the next week etc...let's assume no poor user errors etc.
Then you might be able to say with 95% confidence levels what the errors are or are not with the test kit/method.

That would take too long and cost too much, so simply calibrating each time is wiser.
2 test vs 20-30.

Do not assume because one hobbyist had good luck with a brand of test kit, you will get so lucky.

Think about it like this: would you believe a polling with a smapling no# of one bias person?
Hope not.

Yet, that is what many like to argue.
You need to do more than one replicate for any test to be even remotely confident of the results and say much.
A polling of say 1000 random folks might be wiser............

Or a random sampling of 50 Hagen test kits etc.........

See the differences?

As far as actual uptake, you need to do dry weight analysis of the tissues in the plant to really say much about PO4 uptake, after all..........some PO4 might buind to soil, preciptate out as FePO4, algae uptake, bacteria and fish waste, water changes can export these forms etc. So unless it's really active and rapid uptake, you will not see this too well unless you have pretty artificial and controlled conditions.

Regards,
Tom Barr

 

[SuperColey1]

Tom

Can you explain how to calibrate these kits?

Andy

 

[donkey]

Hi blahblah
hope you dont mind me asking but. is it 3 drops of the two little blue bottles and ten drops of the big bottle. i lost my instructions to my Hagen PO4 test kit.

 

[blahblah]

Thanks Tom for the thorough explanation, I shall have a go a calibrating my own test kit - lets see! It's seems there's no easy method to account for plant uptake, save for dry weight analysis, which sounds pretty complex for the likes of me. But your points on uptake are useful for me to consider. Presuming the test kit passes calibration, then I shall keep going with testing and observing.

Andy, you can find info on the calibration procedure here - http/www.plantedtank.net/forums/water-pa...ant-uptake.html (i hope it's ok to link to another forum) - post no.5.

Donkey, it's 3 drops of each small bottle, and then 1 drop of the large bottle, remembering to cap and shake between each addition of drops.

 

[TribeOfShroom]

Not that I know what you're on about, but seeing as I've got a planted tank I'll ask anyway. What's PO4? Potassium??

 

[SuperColey1]

N = Nitrogen (nitrate/ammonia)
P = Phosphate
K = Potassium

Andy

 

[TribeOfShroom]

Sorted! Although I should really know that, as I grow most of my own crops