Advice on dry ferts. please

L

laka

AC Members
Dec 10, 2006
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Australia
Setting up 6*2*2 ft tank . Substrate 4 inch thick. This leaves 150 US gallons of water. Will be low tec tank heavily planted low fish population with 6500K metal halides 150W*2. 10% water change monthly only.
Nitrates: two teaspoons will provide 12ppm No3 as KNO3
Potassium: 10g gives 7.88ppm K+ as K2SO4.(I have KCl. Is
the above dose valid for KCl?)
How do i measure K+ so i know when and how much to
add?
Like to aim for 4 degrees GH
Dosage for CaCl2 in 150 gallons please?
Dosage for MgSO4 in 150 gallons please?

Phosphates: How much K2PO4 to reach 1-2ppm in 150 gallons?

Without frequent water changes how do i dose potassium? Do i assume a 1:1 ratio with KNO3?
Also how many grams in 1 teaspoon?
Thanks
 
The dose will be different for KCl. Go to Chuck Gadd's web site and download his calculator. Just do a Google search for Chuck Gadd. Unless you burn money to heat your house there are no decent consumer level potassium test kits.

Take a few minutes and read my Guide. I have dosing directions on CaCl2 and MgSO4 in it (I'm too lazy to look it up tonight).

How many grams of what in a teaspoon? A gram is a measure of weight and a teaspoon is a measure of volume. A teaspoon of water will have a totally different weight than a teaspoon of mercury. (crazy example but it makes my point).
 
Rex
I had a look at your site. It gives lots of valuable information but now i am even more confused!!
In your "Water Chemistry" section you state that .33g MgSO4 will raise 10 gallons water to 1 degree and further down in your summary you state 1/2 teaspoon being 2.8g in 10 gallons water will raise Mg levels by 7.8ppm!!

Similar discrepancy occurs with Ca. I suggest you have a look at your site and please clarify. You also state 1 level teaspoon weighs approx. 5.6 g. Is this correct?
 
"The best way to do this is with Epsom salts. ½ of a teaspoon if Epsom salts will raise the magnesium level to 7.8 ppm in 10 gallons of water. Recommended levels of magnesium are 5-10 ppm. If your water has a gH of over 3 degrees you would not normally have to add magnesium.

To sum it up.


To raise gH use calcium chloride and Epsom salts. Add them separately or you will end up with calcium sulfate which takes a very long time to dissolve.

0.79 grams of calcium chloride and 0.33 grams of Epsom salts will raise 10 gallons of water 1° of gH. "


These are your words.

LAKA
 
Rex Grigg said:
Please PM me the links. I can't find the reference to the 2.8 grams. I may be going blind though. Nor can I find the reference to the 5.6 grams in either my Summary or the Water Chemistry page.
Click to expand...

i am blind also because i looked and looked and looked and couldnt find it. on the other hand it wouldnt be the first time i missed something.
 
"For the KNO3 you want to mix 16.8 grams or 3 teaspoons or one tablespoon (did you know there are three teaspoons in a tablespoon?) into 250 ml of water. Each ml of this solution will give you 1.08 ppm of NO3 in 10 gallons of water. Note I did not say in a 10 gallon tank I said in 10 gallons of water. Don't know how much water your tank actually holds? Tough. You will also get the side "

OK GUYS HERE IT IS. rEX IT IS UNDER "DRY fERT DOSING"
I DEDUCED FROM THE ABOVE 1 TEASPOON=5.6g

LAKA
 
You got yourself really confused.

1 teaspoon of KNO3 will be around 5.6 grams.

That doesn't hold true for anything else.

One more time. If it's confusing to you then read it till it makes sense.

A gram is a measurement of weight. A teaspoon is a measure of volume. You can't do a conversion of grams to teaspoons (or any weight to volume) without knowing what substance you are trying to do the conversion for.

A teaspoon of pure water will weigh about 4.9 grams
A teaspoon of sea water will weigh about 5.12 grams
A teaspoon of mercury is around 67.8 grams
A teaspoon of alcohol is 3.9 grams

BTW, the above figures come from http://www.allmeasures.com/formulae/

So you see you can't do a straight conversion of grams to tablespoons. It just doesn't work. So by taking one figure and trying to apply it to something else you confused yourself.


Also there is a difference in ppm and degrees of hardness. So you really got confused. Everything in the Guide is accurate.

Example:

The best way to do this is with Epsom salts. ½ of a teaspoon if Epsom salts will raise the magnesium level to 7.8 ppm in 10 gallons of water.

That statement is accurate.

As is this statement:

0.79 grams of calcium chloride and 0.33 grams of Epsom salts will raise 10 gallons of water 1° of gH.

You are comparing apples and oranges in this case. ppm and degrees. Also by trying to take the density of KNO3 and apply it to another compound you really messed yourself up.
 
Last edited:
Laka sounds like a fun adventure. My only real suggestion is to test, test .test. Soon enough you will get a feel for it. Non of it is all that critical as long as things are in proportion and nothing is lacking. I know people who run very high levels of CO2 with no problems. I run into a lot of people who seem to not add enough KNO3 who wonder why they have an algae problem. I get most of my Mg, PO4 and CA from my water company. I always tell people to ask around and find out what is in the water they have.

Put a grain of CaCl into the kh kit and you will see the color change. Some people say some plants have difficulty with the Cl. I’ve been growing Hygropila difformis recently and some told me that. You might not want to add that twice.

A good substrate will add a lot of micros. Tom’s methods work very well. They are tried and tested.
 
Weight to teaspoon conversions:
Compound grams per teaspoon
Potassium Sulfate 6g (estimated)
Potassium Nitrate 5.6g
Potassium Chloride 6g
Magnesium Sulfate 5.4g
KH2PO4 4.8g



REX Above are measurements CHUCK made and as you can see there is a miniscule difference in weight between the various solids.
So let's do the calcs for my 150 gallon water volume according to your formulae.
NB The only other assumption i make is that 1 degree of German Hardness is equivalent to approx 18ppm of Ca/Mg ions.

"1/2 teaspoon of Epsom salts will raise Mg by 7.8ppm" as you state.
This equates to 1 teaspoon weighing 5.4g of MgSO4 will raise Mg by 1ppm in 150 gallons of water. Do you agree?

Now you then state in your summary
".33g epsom salts raises 10 gallons water by 1 degree GH"

So i calculate that in 150 gallons water i will have 1/15th degree of Mg which is equivalent to saying 4.95g of MgSo4 (ie one teaspoon approx.) will give a rise of Mg by 1 degree.

So in summary the first measurement shows 1 teaspoon to raise Mg by 1ppm and the second measurement shows 1 teaspoon to raise Mg by 1 degree of GH ie. 18 ppm.

So which is correct? Where am i going wrong?

PS You actually state in your second assumption that 0.79g CaCl2 and .33g MgSO4 will raise 10 gallons water to 1 degree GH. Mg being 1/3 of the total mass then 1 teaspoon will raise Mg in 150 gallons by 1/3 degree of GH or 6ppm. Even then there is a discernable difference between the two calcs. based on your rules.

IF this is not correct please explain where i'm going wrong.
LAKA
 
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