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Thread: Toms PMDD style EI dosing Please Help

  1. #1

    Toms PMDD style EI dosing Please Help

    Hi Guys
    I am going to try out Toms PMDD style EI dosing but i have a few questions i hope you guys can answer. its says that if you have a high P04 in the tap water then add less PO4 well mine is 5 coming out of the tap so this means i need to add les to the PMDD. now if my tap water is at 5 what should i reduce it to ?. i also seem to be having problems with my plants there stems are weak and thin and i get lots of leaves that just fall off and float around the tank. now i think this might be because i have a low GH in my tap water its only 2 coming out of the tap. by adding GH booster do you think this would sort this problem out. i have also noticed that i get holes in my leafs as well.

    Thanks guys hope someone can help me out

  2. #2
    If you are testing the tap water for phosphates don't forget that you have to calibrate the test kit first. You need to make some solutions with known concentrations of PO4 and make sure the test kit accurately measures those concentations. You can't assume any test kit will be accurate.

    In order to guess what the problem with your plants is, we need to know how much light you have, what size tank, and do you use CO2, Excel?

  3. #3
    Thank you for getting back to me. i used a Hagen test kit but I'm not to sure how good they are. i am waiting for a letter from my water board co to give me a true reading of my water. the tank is a 60 US gallon and does have co2 30ppm. it has 146 watts of light over it. 2/T5s and 1/T8.

  4. #4
    Ok, you do have high light, so any phosphate in the tap water will not stay in the tank very long before the plants use it. The same is true of nitrates. And, it doesn't matter what brand test kit you use, if you are going to make a critical decision about fertilizing from the test results you have to calibrate it first. I have to suggest that you do the regular EI fertilizing routine.

    How do you measure your CO2?

  5. #5
    Hi VaughnH
    i use a drop checker with some 4 dKH Solution. i got it from AE.

  6. #6
    so should i Reduce the PO4 that i mix in with the PMDD ? and if so by how much

  7. #7
    Quote Originally Posted by donkey View Post
    so should i Reduce the PO4 that i mix in with the PMDD ? and if so by how much
    In my opinion you should just follow the EI dosing, not PMDD, method. That is the easiest way to go, and you can modify it after seeing how your plants react to it. Also, make sure you have good water circulation in the tank, so CO2 enriched water is available to all of the leaves.

  8. #8
    Thanks. do you know of any good Conversion calculator that will go from tp to grams. i don't have any small tp but i do have some digital scales.

  9. #9
    ok i think i have it. dose this sound about right

    add to 500ml of water

    30ml solution or 1/2 tsp KNO3 3x a week
    18ml solution or 1/8 tsp KH2PO4 3x a week
    8ml solution or 1/8 tsp K2SO4 3x a week
    10ml or 1/8 tsp traces 3x a week

    this is for a 40-60 Gallons (152-227 litres)

  10. #10
    Potassium Nitrate - 40g to 500ml of water and adding 10ml per 100L of water would give you a value of 5ppm.
    Potassium Phosphate - 15g to 500ml of water and adding 5ml per 100L of water would give you a value of 1ppm.
    Potassium Sulphate - 55g to 500ml of water and adding 10ml per 100L of water would give you a value of 5ppm
    Magnesium Sulphate - 70g to 500ml of water and add 50ml once a week per 100L of water - this would give a target of 7ppm.
    Trace mix - 15g to 250ml of water


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