I'd like somone to check my EI maths please!!!

Discussion in 'Aquarium Fert Dosing' started by maj74, 4 Nov 2008.

  1. maj74

    maj74 Member

    Ok, I have my first delivery of dry powders arriving tomorrow, and I want to run a possible dosing regime and recipe past people for feedback.

    Introduction: 250l (150cm x 40 x 40) discus tank with medium density planting (it'll grow!), 4 x 54w 120cm T5 plant gro tubes (2 on for 8 hours, 2 for a 3 hour middiay burst), FE CO2 system slowly being increased to 20 ppm (not wanting to go any higher if poss due to the discus.)

    As already discussed in another thread, a 50% water change is not feasable so I shall be trying about 15% 3 times a week.

    Due to this WC regime I realise I shall have to dose a slightly higher rate of ferts, due to some of the previous dose being removed every couple of days. :rolleyes:

    Using James' planted tank calculator, I carried out the following maths:

    I want to prepare 1000ml solutions at a time, dosing 25 ml per dose of macro and trace solutions. (Keep both the same, keep it easy!)

    All the figures below hae been slightly rounded where sensible.

    Macro solution (1000ml):

    Potassium Nitrate 162 g (27 teaspoons) = 3 x 10ppm doses per week
    Potassium Phosphate 29 g (4.5 teaspoons) = 3 x 2ppm doses per week

    The above two amounts also provide 3 x 7ppm doses of Potassium per week.

    Trace Solution (1000ml):

    60g provides correct amounts for 2 x 25ml doses per week.

    These solutions would be used in the following regime:

    Day 1 15% water change followed by 25ml macro dose.
    Day 2 25ml Trace dose.
    Day 3 15% water change followed by 25ml macro dose.
    Day 4 25ml Trace dose.
    Day 5 rest.
    Day 6 15% water change followed by 25ml macro dose.
    Day 7 rest.

    Please can someone who really understands this let me know if this makes any sense at all?! :(

    If it sounds like a reasonable starting point (As I understand that EI is a little bit 'trial and modify') then excellent. If in any respect, I'm not even close, please can I have suggestions! (Please! modifications to the numbers, not a 'do a 50% change' suggestion if at all possible.)

    Because I use only rainwater in the tank, my GH and KH are quite low (3.3. and 1.1 degree respectively), So I'm guessing a GH booster would be a good idea. (Presumably this can be made with Magnesium Sulphate and Calcium Sulphate? If so, what are the figures involved?)
  2. ceg4048

    ceg4048 Expert/Global Moderator Staff Member

    Chicago, USA
    The Nutrient dosing levels look OK to me and I would just add a few teaspoons of MgSO4 every water change and see how things go. You don't need to go crazy adding more TDS then you need for your fish.

    There is an awful lot of light and I can already see CO2 problems coming. If you are concerned about limiting CO2 then you will be doing yourself a favor by limiting yourself to no more than 3 bulbs (and probably only 2 bulbs for the first 6 weeks or so). It's pretty much a self delusion to think you can control CO2 accurately to some target value like "20ppm". It just doesn't happen. Make sure you use 4dkh water in your dropchecker to give you a good idea of the CO2 concentration levels.

  3. maj74

    maj74 Member

    Thanks for the reply. Good to know my maths was reasonably accurate! :D

    Some questions from your response!

    1. So you're happy that I don't need to worry too much about the lowish GH and KH in the tank, as long as I dose with some Magnesium Suplhate? Presumably I can add this to the macro mixture? How many teaspoons would you guess for the 1000ml liquid dosing 25ml 3 x a week? (I think I ordered some with my delivery today anyway, just in case!)

    2.Lighting is 2 or 4 (arcadia unit) so I shall take out the 'midday burst' for now?

    3. Am I right in thinking that I musn't just rely on the drop checker for the co2 level since by the time I get this to go the perfect lime green, I may be causing the discus some problems?

    Many thanks for your time and thoughts... this is an excellent forum!
  4. ceg4048

    ceg4048 Expert/Global Moderator Staff Member

    Chicago, USA
    Hi maj,
    From a plant standpoint both GH and KH are highly overrated. Having said that though it's important to understand what it is about the two that are relevant in the first place. The trace elements that are necessary for plant growth are substances like Calcium and Magnesium. These substances directly influence the GH because GH is a measure of the Calcium and Magnesium salt content. The thing is that plants don't need nearly as much Calcium as they do Nitrogen for example. The difference in nutritional requirements is at least an order of magnitude. The same for Magnesium. A little goes a long way and values can be very small. The only reason we wind up adding so much MgSO4 is because Magnesium makes up only about 20% of the weight of an MgSO4 molecule so you wind up having to add 5X as much powder to achieve any target level of Mg. All that powder adds massive levels of TDS so from a Discus or softwater species standpoint you only want to add the amount of Mg that you can get away with. In fact all the dosing salts we add increase the TDS so if this is something that is important to you then you'll have to pay attention and try to stay on the low side of dosing. The EI concept of "Go for Broke on nutrient levels" conflicts with the imperative of minimizing TDS. On the other hand, unless you intend to breed the Discus in the planted tank the TDS value isn't really all that big of a deal anyway, in which case having clean, well oxygenated waters tops the list of priorities. So plants, for the most part, don't really care about any intrinsic or physiological impact of GH or KH - they only care that they get fed, period. If getting fed results in a sharp rise in GH/KH the plants can get over that fact. If they can be fed adequately while at the same time maintaining a low GH/KH then they can live with that as well. Therefore do not try to optimize your tanks GH/KH thinking that you are doing the plants a favor. There are a handful of plants that actually require low TDS. The rest do well under either high or low TDS - as long as nutrient levels are sufficient.

    I would definitely delete the burst for now. Midday burst and midday siestas are all illusionary concepts. Siestas are a drag on food production and bursts can cause trouble if their intensity is too high, which typically results in CO2 shortages. The impact is starvation and algal blooms. My preference is to lower the environmental pressure by keeping the lighting reasonable and getting a handle on the technique of CO2 injection and control. Tiny flaws in your CO2 technique can cause big problems. These problems are further exacerbated by high intensity light. Having said that I do add my light in stages throughout the day - I just don't think of it in such absurd marketing terms. The fact is that CO2 assimilation is at it's most crucial early in the photoperiod. That is when plants need CO2 the most. If the lighting is too high this causes problems. By keeping the lighting lower in the first couple of hours it allows proper buildup of CO2 concentrations while keeping the demand for CO2 assimilation low at a point in the photoperiod when the plants are most vulnerable to inefficient CO2 delivery/uptake. The mantra that more light drives a demand for more CO2 is a good one to remember and will keep you out of trouble. :idea:

    I agree that you should not just rely on the dropchecker. The checker requires a couple of hours to respond to any changes in CO2. For £1000 you can buy a reasonably accurate CO2 meter that gives you a reading within minutes. I'd rather make that mortgage payment with that amount of dough. As a cheaper alternative, regularly monitor the bubble rate, as well as fish behaviour and plant growth to give you a more comprehensive idea of the CO2 status.

    Glad you find the forum useful. :D

  5. Mark Evans

    Mark Evans Expert

    newark notts.
    bravo ceg. i don't even have a drop checker any more.i just do the above. :D

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