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Why dry dosing?

Discussion in 'Advanced Strategies and Fertilization' started by tanksalot, Mar 18, 2006.

  1. tanksalot

    tanksalot Junior Poster

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    I've read a number of threads suggesting fish feeders as dry fertilizer dosers, and see that in the estimative index dry amounts are specified. Since I make (and have extensive access to) digital dosing pumps, I'm curious why the focus on using dry materials? Is it primarily for individual component control? Even without a digital pump, a simple small peristaltic pump and a timer should be a pretty hassle-free way of dosing a diluted mixture of additives.
     
  2. Spar

    Spar Guru Class Expert

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    Re: Why dry dosing?

    not many people would be willing to put money into a pump to do the dosing. and then you would have to have 2 of them anyway since you shouldn't be dosing traces (iron) and PO4 at the same time. so I would say that dry dosing is meant for individual control of what goes in the tank, as you said above.

    i am interested however in the pumps you are referring to. can you post some pics of the setup you have?
     
  3. tanksalot

    tanksalot Junior Poster

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    Re: Why dry dosing?

    Cliff:

    I sell them at http://www.innovativeaquatics.com (used). I also sell them new at http://www.reefdosingpumps.com, but that's very pricey.

    You said "since you shouldn't be dosing traces (iron) and PO4 at the same time".

    Since my background's in chemistry, I'm ashamed to ask "why not".?

    I suspect the pumps I have aren't totally suitable for aquatic plant applications, but some modifications might be possible. I also have noticed what you had going for systems and am impressed. Very ambitious.

    Stan F.
     
  4. pigwiggle

    pigwiggle Junior Poster

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    Re: Why dry dosing?

    I believe the idea is that the trace chelating agent precipitates some of the macros. There certainly is a precipitate when I mix trace and macros although I’m not exactly sure what it is. Doesn’t matter really; it’s something I want dissolved in the column and it’s not.
     
  5. Laith

    Laith Lifetime Charter Member
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    Re: Why dry dosing?

    In high enough concentrations, Fe and PO4 precipitate out as FePO4. Don't ask me what those concentrations have to be for this to happen ;) !

    According to Tom, Fe is sometimes used in natural water systems (lakes etc.) to remove PO4 by precipitation...
     
  6. Tom Barr

    Tom Barr Founder
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    Re: Why dry dosing?

    Sure, they can be used.
    I use them on client tanks.

    One thing is dry dosing makes it easier for most folks.
    Not eveyone is going to buy such a dosing pump.

    Not everyone has a scale to weigh the mass out of the ferts, so teaspoons work pretty good.

    But also making the proper mixture to dose and the time also makes things sort of diffcult for folks, I simply do this: take what I'd normal dose over 2 weeks, add the two weeks worth of ferts to the reservior + a little more water than the dosing pump would dose over that time(say 50mls a day x 14 days= 700mls+50mls just in case)
    Keep the trace/PO4 apart.

    They will preciptate depending on the chelating/complexing agent.

    Regards,
    Tom Barr
     
  7. tanksalot

    tanksalot Junior Poster

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    Re: Why dry dosing?

    Thanks everyone for the replies, and most importantly, for the development of the Estimative Index. I've had a planted aquarium in my sunroom for years, with a built-in overflow to the outside, float switch for automatic refilling, pressurized CO2 with controller, and it's located right next to a window. I've had, at best, mediocre luck at having it be an attractive planted tank, with severe algae problems, great growth with some plant species (Vallisineria primarily) and only so-so growth with most others. I'm very much looking forward to implementing the EI concept and seeing how it looks. To KNOW the cause of the problems I've had and have a known method of achieving my goal is terrific!

    Stan F.
     
  8. Tom Barr

    Tom Barr Founder
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    Re: Why dry dosing?

    Generally folks that have had previous plant experience do very well with EI.
    New folks, well, they have a number of issues to learn and get a good feel for.......it just takes some time.

    But it's tough to get things easier without going to non CO2 methods and/or lower light.

    Regards,
    Tom Barr
     
  9. a1matt

    a1matt Prolific Poster

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    I am dry dosing manually, and would really like to dose PO4 and Fe on the same day (I have a low light tank and am working towards dosing once a week). Can I do this? If so how close can I get away with? hours, minutes even? Will I visibly see the precipitation if I get it wrong or not necessarily?

    Also! When doing water changes I add my water conditioner straight into the tank. Will this take out some of my nutrients? I know it is designed to remove nitrates, but what about any others? and should I wait a certain amount of time after dosing that before adding my dry ferts?

    Sorry for my flurry of questions today, I did have a search of the forums for a while before posting!
     
  10. a1matt

    a1matt Prolific Poster

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    BTW As an addendum to my last post I am curious to the science and not just looking for instructions... I wonder if the phosphates need to just dissolve into the water, or whether it has to be used up completely by the plants before adding the iron.
     
  11. VaughnH

    VaughnH Lifetime Charter Member
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    A water conditioner, actually a dechlorinator, such as Prime is intended to neutralize the chlorine and ammonia in tap water, not to remove nitrates. If you dissolve phosphates in water, then add chelated iron, you get a cloudy mixture containing a precipitated Iron phosphate compound. If this is done in the aquarium, the precipitate settles on the substrate, where it is eventually available to the plants. But, we want it to be available when we dose it, so we don't want to dose phosphates and iron at the same time.
     
  12. fishyio

    fishyio Lifetime Charter Member
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    I have a question on the Iron/ PO4 thing. If you have a fancy substrate which are often sold as containing high levels of iron, is there a danger that the huge reservoir of iron locks up all the phosphate you are adding to the tank when dosing?

    I will add some figures here, in case it makes any difference. I'm adding 1/16th teaspoon potassium phosphate twice a week to a 22 US gallon tank, 85 litres ish. My tap contains about 0.7 ppm in it's own right (based on test kit....:rolleyes: ) 50% change once a week.

    I forget what my substrate was called - AquaPlantoSurge or something similarly silly but it it is a UK plant substrate for aquariums comprising white/black/grey grit stuff which is so iron rich that some bits leap onto the magnetic glass cleaner if it goes too close.

    Any thoughts from chem boffins welcome
     
  13. Tom Barr

    Tom Barr Founder
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    Ideally a high Fe substrate will bind PO4 for a time, but the sites will fill up after a while and then not matter unless they are released through low redox/O2 levels and the Fe and PO4 are released and leak out of the substrate, or are taken up by plants which actively reduce these FePO4 complexes into bioavailable forms.

    So it simply may act as temporary storage for PO4 in the sediment for plant roots etc if there's none in the water column etc.

    Regards,
    Tom Barr
     
  14. fishyio

    fishyio Lifetime Charter Member
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    Interesting. I have only recently started using the EI and I still feel the need to comfort myself with the odd test kit. Last week I was adding Phosphate and testing, before, and then after half an hour or so, to see if the dosing calcs were giving me a reasonable concentration.

    I noticed that I couldn't detect the great change the fertilizing calcs were suggesting.

    I was thinking this could be a) rubbish test kit (imagine) b) poor calcs c) the dry potassium phosphate I was using was odd, or fake, or had some other problem.

    Might it be that the PO4 was going straight into the iron rich substrate and thus not appearing in the water column concentration test?

    From what you have said Tom, I guess that wouldn't be such a problem since the plants could still get at it via the substrate, so as long as I keep adding it into the tank it'll be fine, regardless of the water column concentration reading?

    Suddenly the "throw out your test kits and look at the pesky plants" philosophy starts looking more and more sensible !!
     
  15. Tom Barr

    Tom Barr Founder
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    Well, you can give up and do that, but you can also do some easy little test also to see about this.

    Take a few gallons of tank water, add say 2ppm of PO4 to this.
    Add the Fe.

    See if the before and after Fe dosing does anything to PO4.
    Wait 30 minutes after mixing them.

    You do not have to do this inside the tank is my point.

    The issue is likely a relative one with the test kits and it should be able to detect PO4 at 2ppm, at least I'd hope so...........

    Junky kits cause more issues than they solve.

    Regards,
    Tom Barr
     
  16. fishyio

    fishyio Lifetime Charter Member
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    Thank you Tom for pointing out the obvious answer - "try it out and see"!

    I did the experiment and the PO4 test did not show any darker blue colour than 0.7ppm even when I chucked phosphate in by the handful (well almost). So it has "gone off" in the 6 months since I bought it.

    I bought a fresh kit and found my tap water is 2.5ppm, the water in my tank was actually nearer 5ppm...of course it's still only another test kit but hey..

    This little practical experiment has confirmed to me two things which I know you have mentioned repeatedly on this site,

    Firstly you have to be very suspicious about test kits (especially that they change over time)

    Secondly an excess of Phosphate does not automatically cause an algae apocalypse as everyone in every LFS etc maintains. I have been dosing up Phosphates to about 5ppm while reading 0.5-0.75 on the test for a few weeks now. I must be one the few fools who have actually done this heretical thing in their precious aquarium.

    I can report that I have a tiny smattering of BBA here and there on the odd leaf, but the tank is looking better than I've ever managed previously, by following your advice about plenty of CO2 and a weekly water change.

    Thanks again for the advice
     
  17. Tom Barr

    Tom Barr Founder
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    Tap often has PO4.

    That's how we discovered why my tanks did so much better with so many plant species, my tap had 1.1-1.2ppm of PO4.

    We called up the utility, then measured with a Hach PO4 test kit and a Lamotte test kit.

    We should have made a reference solution as well, but did not.
    Anyway, Steve's tap has zero PO4, and so he started adding KH2PO4 after seeing my tanks in disbelief.

    He could estimate how much PO4 he was adding via mass and volume, no dosing calculators where around back in those days!
    Those levels matched with the estimation using the test kits.
    So we had some confidence.

    As far as heresy, well, it takes over 10-20 years to change things in the hobby.
    It's been about 10 years now since folks have been adding PO4, at first most where pretty conservative, as sloppy folks started doing things(about 7years or so ago), we noted that even 1.5-3ppm ranges also had better effects on some plants and on Green spot algae.

    So now most go with 2ppm as a range target.
    You can add more, but it does no good really.

    The best approach to the guys at the LFS's, bring in lots of plants to trade and pretty pictures.

    Tell them how is it that you add all this PO4 raw into the tank and why don't you have algae if what they say is really true?

    I mean let's be honest, if someone suggest that excess levels of PO4, and just that, nothing else is causing the algae, then we shouild be able to add lots of PO4 and => get algae.

    But we do not so how can we believe that hypothesis?
    We cannot.

    Try it and see.
    Tell them to do the same.
    Do not guess and assume, that's not any good.
    Same deal with a test kit, do not assume and guess they are okay or not, try it and see if they are by using a known amount of PO4.

    This is what researchers must do when they take their measurements.

    But all the hacks that whine and complain that EI is bad, shot in the dark etc cannot suggest how to calibrate a single test kit, a bit ironic ain't it? :cool:

    Knowing a little is more dangerous:rolleyes:
    Sad thing is, many never get beyond just knowing a little.

    Look at both sides of this issue, I know it's easier from a management perspective to not test and use water changes to re set the tank. And if I do test, I use the test kits that are the best there are and that I calibrate myself.

    That way all that work/labor and $ is not wasted.
    I also test intensively when I do test.
    It's too much work and labor to test continuously like many folks suggest that you do, but of course they admit later that they do not test unless there's an issue or they only measure one main parameter.
    You have to take your own advice, which many do not.

    I like to test for most issues in 1-3 week blocks.
    I slack off after that unless it's a job where I'm getting paid to do it etc.

    1-3 weeks is the typical time it takes to turn a tank around from a bad terrible state to a nice healthy one.
    So I can correct things and send them on their merry way in this time frame.

    Your tank: CO2, CO2 and CO2.
    Trim off any BBA.
    The plants will grow back and some CO2 tweaking is all you need from there.

    Regards,
    Tom Barr
     
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