Using PMDD with EI dosing - The Planted Tank Forum
 
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post #1 of 14 (permalink) Old 01-15-2010, 08:16 PM Thread Starter
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Using PMDD with EI dosing

So I've been reading everything I can on Ferts to try to get a handle on things but I've noticed some major inconsistencies. I don't have easy access to dry ferts where I live so I bought some PMDD online. The ingredients of which are as follows (as posted on the Aquabotanic site):

1 Tbsp ~9g Chelated Trace Element Mix (7% Fe, 1.3% B, 2% Mn, 0.06% Mo, 0.4% Zn, 0.1% Cu, EDTA, DTPA)
2 Tsp ~14g K2SO4 (potassium sulfate)
1 Tsp ~6g KNO3 (potassium nitrate)
2.5 Tbsp ~33g MgSO4.7H2O (fully hydrated magnesium sulfate, aka epsom salts; omit if already present in trace element mix)
300mL distilled H2O

I have a 30 gal tank so for the EI dosing method I need

+/- tsp KN03 3x a week
+/- 1/16 tsp KH2P04 3x a week
+/- 1/16 tsp (5ml) Trace Elements 3x a week
50% weekly water change

So my problem is if I mix 1 tbsp of the chelated trace elements mix into 300 ml of water that's equivalent to 3 tsp or 1 tsp/100 ml. To get the 1/16 tsp suggested by the EI method I need 6 ml 3x a week. However, if we break down the KNO3 by the same logic 1 tsp in 300 ml means I need 75 ml to get the 1/4 tsp recommended by the EI method.

To top it all off the Aquabotanic site suggests a "a few drops per 10 gal, every few days or daily" So there must be something I'm missing or my logic/math is way off. I noticed that there are different ingredients to the PMDD than suggested by the EI method so maybe the extra ferts (Potassium Nitrate and Epsom salts) reduce the amount of KNO3 and CTEM required but it still seems way off to me.

Any help understanding this would be greatly appreciated.

Thanks
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post #2 of 14 (permalink) Old 01-15-2010, 08:26 PM
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Why don't you buy the dry ferts online if you're able to get PMDD online? I don't have an answer for you, but was just curious why you can mail order one but not the other.

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post #3 of 14 (permalink) Old 01-15-2010, 08:39 PM
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I see nothing wrong with that amount of trace used for EI.
EI is assuming you have a max growth, or it is a non limiting value, much like modified hogland's solution is for hydroponics.

You start there and can reduce it if you have lower light, no CO2 etc etc, => common sense.

If you have higher light or not, and CO2, and you do the water changes, then nothing will build up either way, if you reduce the dosing to suit the tank, that will reduce the build up and perhaps you can skip a few water changes, but these routines both work.

PMDD on the other hand, was developed with low light and assumed that you have enough PO4 from the fish and tap water. So low light, low demand, good fish load and feeding etc, made the system work fairly well.

When you add more light, this means more CO2 and more nutrients, so the fish waste typically will not keep up.

A PMDD version of EI can be seen here:

http://www.barrreport.com/showthread...tyle-EI-dosing

Some find dosing daily suits their habits.
I'd suggest using less light and work on that and CO2, then focus on tweaking nutrients last.

Many folks , particularly new or intermediate spend a lot of wasted time playing with nutrients and not enough on the basics, balance the light/CO2, do routine care, aquarium maintenance.

Once you realize that, then things are much easier and simpler to resolve.

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post #4 of 14 (permalink) Old 01-15-2010, 09:47 PM Thread Starter
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Quote:
Originally Posted by 2wheelsx2 View Post
Why don't you buy the dry ferts online if you're able to get PMDD online? I don't have an answer for you, but was just curious why you can mail order one but not the other.
I could but I got the PMDD (for $5) when I got some plants for no added shipping. I'm just getting into planted tanks and the PMDD seemed much easier and less complicated (to a noob).

Tom, I wish there was an icon for "hitting the nail on the head". I got the PMDD about two months ago, before I got a test kit suitable to determine my CO2 levels. I've since discovered that my CO2 is in the single digits and have parts for a DIY system enroute. I didn't think the CO2 was necessary initially because I only have 1.9 WPG but I've been battling BBA so I thought I'd add it too.
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post #5 of 14 (permalink) Old 01-15-2010, 09:52 PM
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If your tank is small enough (like 20 gallons or smaller) I'd just go the Excel route rather than DIY CO2. A lot of hassle I found. My tanks are either pressurized or Excel only.

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post #6 of 14 (permalink) Old 01-15-2010, 11:20 PM
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Quote:
Originally Posted by 2wheelsx2 View Post
If your tank is small enough (like 20 gallons or smaller) I'd just go the Excel route rather than DIY CO2. A lot of hassle I found. My tanks are either pressurized or Excel only.
+1 for smaller tanks for many, as long as they can dose and are considering a daily routine anyway.......

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post #7 of 14 (permalink) Old 01-15-2010, 11:29 PM
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You might find this article of use as well, it was before EI and after PMDD, around 1996, Steve and I discussed this a fair amount at the time:

http://www.barrreport.com/showthread...and-parameters

Even back then, we both agreed on Lamotte and Hach test kits and using some reference to ensure the test kit was correct. I consider Steve my "aquatic plant father" in some respects for arguing the need and utility for such methods in answering aquatic plant questions.

I went much further later, but the impression was in place back then.

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post #8 of 14 (permalink) Old 01-16-2010, 12:43 AM Thread Starter
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Quote:
Originally Posted by 2wheelsx2 View Post
If your tank is small enough (like 20 gallons or smaller) I'd just go the Excel route rather than DIY CO2. A lot of hassle I found. My tanks are either pressurized or Excel only.
Actually I have a 30 gal. and no funds for a pressurized system (nor do I think anywhere to fill it within an hours drive).

Tom, thanks again for the great links.

So let me get this straight. Since my town water comes out at a pH of about 6.8, then if I increase the KH (by adding baking soda) to between 3 and 6 (it comes out just under 2 degrees) then I'll have the CO2 I need without any kind of supplimentation? (see Rex's Planted Tank Guide CO2 Chart)

To take it a step further, if I shoot for a KH of 5 or 6 then as the pH increases throughout the day, it'll stay in an ideal range of CO2 levels. Seems too easy.
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post #9 of 14 (permalink) Old 01-16-2010, 12:50 AM
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Changing your kh doesn't magically give you co2. You have to add co2, to get more co2.

The chart you are looking at assumes nothing else is effecting your kh. It is NOT an accurate chart for use in aquaria.
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post #10 of 14 (permalink) Old 01-16-2010, 04:09 AM Thread Starter
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Doesn't increasing the KH for a given pH increase the ability of the water to hold CO2 that it gets from the fish/plants/atmosphere? Aren't those sources sufficient to increase the CO2 without using supplimental sources?
Could the NaHCO3 or CaCO3 break down to form CO2 as well as some other compounds? Similar to how the plants get both K and NO3 by breaking down KNO3. (I guess that's closer to Chemistry than magic )
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post #11 of 14 (permalink) Old 01-16-2010, 04:21 AM
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Quote:
Originally Posted by Tuiflies View Post
Doesn't increasing the KH for a given pH increase the ability of the water to hold CO2 that it gets from the fish/plants/atmosphere?
No, it doesn't.
Quote:
Aren't those sources sufficient to increase the CO2 without using supplimental sources?
No, they aren't, unless you have a low light tank.
Quote:
Could the NaHCO3 or CaCO3 break down to form CO2 as well as some other compounds? Similar to how the plants get both K and NO3 by breaking down KNO3. (I guess that's closer to Chemistry than magic )
No, they won't. When you add CO2 in solution with the water, the carbonates, the carbonic acid, and the dissolved CO2 establish an equilibrium among themselves, which is what the chart of ppm of CO2 vs KH and pH is based on. But, for a given amount of CO2 in solution, that mix is in equilibrium, so it doesn't change until the amount of CO2 in solution changes.

This is a simplification, of course. For one thing, the equilibrium mix doesn't occur instantly with addition or subtraction of CO2, it takes some time. And, in an aquarium the amount of CO2 in solution varies all over the tank, from possibly being low where there are fast growing plants, to possibly being high right where the CO2 enriched water enters the tank.

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post #12 of 14 (permalink) Old 01-16-2010, 04:23 AM
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No. You are reading this chart wrong. The chart implies that if you have a set of kh/ph values, and you monitor them for change. SO start with baseline, then add co2, and then measure again and then you have your hypothetical co2 level(other factors are pertinent, tannic acids, etc).

You can not change the kH or pH and expect that it changes the Co2. What it does is change your starting point on the chart.

If it were that simple, no one would use co2 tanks.
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post #13 of 14 (permalink) Old 01-16-2010, 05:07 AM Thread Starter
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Ahhh, I think I'm starting to see the light.

Thank you both.

So Hoppy since I have only 1.9 WPG do I need supplimental CO2? Or better yet will it help much, even if it's not needed?
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post #14 of 14 (permalink) Old 02-13-2010, 09:03 PM
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I have a low light tank, 3.5 wpg max. I had chronic problems with BBA until I dosed with KNO3 (potassium nitrate). Found it at Lowe's, Spectrice stump remover is 100% KNO3. You have to dilute or will kill fish. At Rex Griggs site can find info on how to dilute it.

Got a picture of the tank?

You haven't posted since Jan. Any improvements with the BBA?

I too think you should just stick with Excel with that low light.

Have read that mulm in the substrate decreases need for carbon. An experiment I am working on.
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