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EI Calculations don't make sense

Discussion in 'Talk to Tom Barr' started by MacFanMr, Oct 5, 2008.

  1. MacFanMr

    MacFanMr Prolific Poster

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    I operate 20+ tanks and have been dosing PMDD. While initially I had more naturally occurring phosphates than was reasonable, as my plants grew in, I began to notice that phosphates dropped off, at times reading zero. I mixed a solution and was dosing that as needed, but didn't feel like it was very consistent.

    So I'm switching to EI. I went through the information available and created a dosing plan. Since my calculations are based on my 240g tank, I will focus on that. The provided sample dosing only went to 100-125g so I simply doubled that to get a dose of 1 Tbsp KNO3 and 1 tsp KH2SO4 three days a week and 1 tsp CSM+B on opposite days with nothing on Saturday.

    I am only able to do a 20% water change on that tank at any one time due to the amount of water I can store in my tank from my RO unit so I was trying to figure out how many of those water changes I would need to do each week to keep things under control. I also have a 60g tank I'm using to grow out Discus fry and do near-daily 50% water changes so need to figure out how much more to dose to maintain the appropriate levels. I read some of the more detailed information about uptake of the various elements and attempted to produce a spreadsheet that would allow me to calculate it.

    The calculated volume of the tank is 218g minus decorations, but I have a refugerium-style 20g tank I use for breeding and a bog that I pump water up into so I left it at 218g. According to Chuck's calculator, those dosages are 12.48ppm for Nitrates, 7.88ppm Potassium, and 4.06 ppm Phosphates. I guessed at approximate starting values based on what I was aiming for with PMDD. I found the uptake values from the thread in the EI section and picked middle of the range for those. To check my formula, I stuck wth the 50% weekly water change.

    So my formula is:

    (existing concentration * (1 - water change percentage)) + today's dosage - today's uptake

    Assuming I've read things correctly, I'm supposed to dose that 3 times a week, but based on that and the numbers I've come up with, I'm looking at 30-50ppm Nitrates and 13-20ppm Phosphates which doesn't seem right at all.

    I've attached my spreadsheet. The dosing plan is on the first sheet, the calculations are on the second sheet. At the bottom of the calculations I graphed it and got a graph that becomes consistent but seems to indicate very irregular concentration levels. But I did read that uptake isn't really constant, so that much may not be important. My bigger concern is that I'm massively overdosing my tanks. I've only been at it for 3 days so I don't think I've done any damage yet.

    Michael
     
  2. Tom Barr

    Tom Barr Founder
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    Well, it assumes that there is a certain amount of uptake.
    If you assume not uptake and add 20ppm of NO3 per week and change only 20% of the water weekly, then the upper bound will be much higher than if you changed 50% weekly(if this case it's 2x the max weekly dose, so 40ppm would be the highest with 50% change and 20ppm of NO3 dosed per week)

    The upper max range will go up as you reduce the % water change.
    If you did 100% water change weekly, then the max upper range with 20% dosed per week = 20ppm obviously.

    50% is nice as it makes the math easy and it is a good amount for most folks to change out. I'd get more tanks for RO or larger ones, or consider more frequency, say 3x a week 20% and dose after each WC.

    Otherwise, EI is less suitable for you if you toss the test kits.
    What you can do is use calibrated Lamotte test kits and dose accordingly and adjust the EI dosing to suit your tank. Traces/PO4/K+ can be higher and you can adjust the KNO3 dosing easily.

    Trade off is testing.
    I prefer cleaner water and more % change personally than 20+ tanks and test. But that's one method to get around it.

    Regards,
    Tom Barr
     
  3. MacFanMr

    MacFanMr Prolific Poster

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    I'm certainly not against water changes, but my 55g drum allows me at best a 20% water change on my 240g tank. So I do more than one water change per week on it, but my goal was to figure out precisely how many I needed. I do water changes nearly every night on one or more tanks as my water supply allows.

    One of the posts in the EI section mentioned that a heavily planted, high light tank would consume 1-4ppm of Nitrates and 0.2-0.6ppm Phosphate per 24hrs so that's where I got those numbers. Maybe I misunderstood and the values should be higher. I'll try using a percentage of the dosage instead.

    Michael
     
  4. VaughnH

    VaughnH Lifetime Charter Member
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    The EI dosing method is built around keeping enough of all nutrients in the tank at all time so that none will ever limit the growth rate of the plants. And, to avoid building up far too much of any of the nutrients from dosing so much, we do 50% weekly water changes. There are other fertilizing methods that attempt to closely match the available nutrients to what the plants are consuming. Those methods can involve a lot more work, much of which is water testing, but if that doesn't bother you you could try one of those methods.

    Just out of curiosity, why do you use RO water?
     
  5. Tom Barr

    Tom Barr Founder
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    I guess my real question backing up is why are you using RO water?
    It's not needed for plants...............so it must be a fish issue?
    I generally have folks blend RO and tap so they do not need as much RO and then do not need to add as much GH and KH for reconstitute.

    RO offers no real solution other than more work for plants.........with a small exception to a few species that are eclectic. Mostly it's an issue of less KH.

    If you used 1/2 RO and 1/2 tap, now you can do EI pretty easily.


    Regards,
    Tom Barr
     
  6. MacFanMr

    MacFanMr Prolific Poster

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    I should clarify, where my title says the calculations do make sense, I'm referring to my own, not the concept of EI or the dosage recommendations provided. I was trying to take those recommendations and adapt them to my own situation and needs and the numbers I was getting seemed wrong.

    I used tap water at a house I lived in when I initially began serious planted tanks. There, my pH was around 7 and the water tasted fine. I moved for work and now live in a loft in a building that is 100 years old downtown in a city an hour away. When I moved in, I experienced a lot of trouble re-establishing my tank, esperiencing a lot of fish deaths even though I took it down and set it back up the same day and even brought 55g of water from the original tank. Upon testing the water, I found it was pH 8.5 and the hot water in particular smelled of chlorine and/or sulphur depending on the day.

    With the replacement of the building's shared water heater and some other work, some of those problems have gone away. But in the meantime I have constructed a system that serves me well but is all RO. The RO system dispenses into a 55g tank with auto-shutoff. It has a heater to pre-heat it. Then there is a pressure activated well pump that pumps it from there to the various locations where I have tanks setup. My 240g has an auto top-off system.

    For water changes, I have small trashcans with sump pumps in them that I drain water into and it in turn pumps the water to the nearest sink as needed. The 240g has a drain plumbed into the tank so I just turn off the auto-refill and my mechanical filter (it uses an intake at the top of the tank) and open a valve for 25min, close it, plug in the refill until it is full, then plug in the filter. So with the exception of a 12g nano in my bedroom and a 72g bowfront in the kitchen, water changes are really simple, but are limited by RO production. I have dual 75gpd elements so I can fill the tank a few times a day, and have found I can do a change when I get home from work and another before bed.

    I have been dosing KH (baking soda) and GH (barr's GH booster) somewhat randomly in the past but have looked up proper dosages (I hope) of 1Tbsp GH booster to add 2 degrees GH in 20g and 1.5tsp baking soda to add 4 degrees KH in 20g. I'm currently raising some Discus fry in my 60g tank and the daily 50% water changes involve adding a lot of GH booster and it takes a while for it to dissolve which is annoying but I would rather dose dry if I can than have to maintain multiple liquid solutions.

    I guess it wouldn't hurt to re-test the water as it does seem better since I moved in 3 years ago. I just figured it was better to work with a known, consistent quantity.

    Michael
     
  7. VaughnH

    VaughnH Lifetime Charter Member
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    Using Prime, or another good dechlorinator/chloramine remover, any tap water that is safe to drink is adequate for fish and plants. Couldn't you solve your water "shortage" problem by some minor plumbing changes on your refill system, so you are using a mix of RO and tap water? If the tap water flow rate is small enough a carbon "whole house" filter will remove the chlorine/chloramine from the tap water as you use it. That is what I use on my refill system.
     
  8. MacFanMr

    MacFanMr Prolific Poster

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  9. Tom Barr

    Tom Barr Founder
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    Okay, you might simply just use an activate in line carbon filter and blend.
    The pH is not of concern, what is, is the KH.

    Is the Kh the same?

    Is it the same from the past location?
    Pipes, old building etc should not influence this.
    Only water source.

    As far as re establishing tanks after moves............this often has nothing to do with source water................even if the source is the same, I've done this and so have many.

    I suppose you could do 3x a week 20% and get close, but that's a lot of water changes. Better to see if the KH is the same and if so, install a carbon filter in stead of an RO.

    Then you can simply use tap for temp adjusted tank water refill.
    Squirt dechlor, however, carbon filters, which you have on the RO anyway, remove that and sulfur/taste and odor issues with tap.
    But unlike RO, there is no waste water, and you can flow it through directly.

    Regards,
    Tom Barr
     
  10. VaughnH

    VaughnH Lifetime Charter Member
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    That is a spectacular tank! May I copy that photo to use for plant club flyers, cards, or whatever advertising stuff comes up? I think most people start setting up a planted tank just dreaming of ending up with something like that.
     
  11. MacFanMr

    MacFanMr Prolific Poster

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    Sure. In fact, I can provide you the original full-size images. There are more pictures (and more to come) at our blog on the topic: An Aquatic Obsession Let me know which photos you would like.

    Michael
     
  12. VaughnH

    VaughnH Lifetime Charter Member
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    Thank you! I am always alert to photos of a planted tank that show what can be done with plants, but aren't so esoteric as Amano's tanks, so someone can visualize himself doing that too. Occasionally I make flyers for our Aquatic Plant Club and leave them in LFS to attract new members. That is where I would use this. I just copied the photo from the first website you linked to that had the picture. It will be just fine that way.

    Your tank just struck a very responsive chord for me! Thanks again. By the way, that blog looks interesting too.
     

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