# QUESTION: Mg and Ca dosing help needed.



## fastang80 (May 7, 2008)

Hi, I am currently dosing MgSO4+7H2O (Epsom salts) following the PMDD formula, but I am still confuse on the fact that if I dose Mg and no Ca wouldn't that cause a Ca deficiency due to excess Mg compare to Ca. By the way I have soft water 3 KH tap water and I am not sure on the GH because my AP test kit does not seem to work, I've added over 25 drops of the reagent and no change in color, the only results I have are from a test strip that showed around 80 ppm, but we all know how unacurate those test strips really are. I am about to purchase some KH2PO4 Phosphate the missing component on the PMDD formula and I wanted to be sure I did not need any CaCO3. I appreciate you input on the subject. Thanks


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## bigstick120 (Mar 8, 2005)

What size tank? How much light? I find that even dosing small amounts of Mg, and Ca help plants. I have soft water as well


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## fastang80 (May 7, 2008)

Tank is a 55g with 4X65w power compact unit with 1+ year old bulbs, they have loss some of their intensity but I am about to purchase some new replacement bulbs. Thanks


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## TimboJones (Feb 29, 2008)

Ca:Mg at 3 to 4:1 as far as I know seems to be acceptable to adjust your Gh. 

I also use the AP Gh test and I have found that the change from yellow to green is very subtle around 3 which I also have. So I try to view the change in very bright light and its easier to see the color change looking down through the top of the tube. saves on reagent too!

I'd also like hear other peoples thoughts!


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## ray-the-pilot (May 14, 2008)

*I believe I had a problem with this test as well*

The test goes from orange to green. When you have a very low hardness adding the first drop will show as green but when you swirl it the reagent changes back to orange. This is not the end point.

OK what I did was think that the test endpoint was when the color changed from green to orange (I know that is stupid but it is an easy mistake) so I kept adding solution looking for a green to orange change.

Here is what you need to do to get a correct result:

Add one drop of the titration reagent and invert the tube. If the solution is green your hardness is less than 1deg. If it is yellow, add the second drop. Continue until the solution turns green when you invert it.

If you have very low hardness you can increase your sensitivity by starting with more water. If you use 10 ml instead of 5 ml it will take 2 drops of reagent to get a color change with 1 deg. water. In that case 1 drop = 1/2 deg hardness.


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## fastang80 (May 7, 2008)

Ca:Mg at 3 to 4:1 as far as I know seems to be acceptable to adjust your Gh.

TimboJones I understand the Ca:Mg ratio but what I am trying to find out is if a GH of around 4-5 has enough calcium. The problem that I am having is that I dose Mg and no Ca at all, it is my understanding that all nutrients need to be balanced and I do not want to create a Ca deficiency by over dosing Mg because of not sufficient Ca with a GH of 4-5 (supposedly).

My other issue is that my GH test stays Orange and never changes color to Green no matter how many drops of the reagent I add, tested twice and both times I stopped at around 25-30 drops because I knew there was something wrong and I did not want to waste the entire reagent.

Thanks


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## fastang80 (May 7, 2008)

The test goes from orange to green. When you have a very low hardness adding the first drop will show as green but when you swirl it the reagent changes back to orange. This is not the end point.

ray-the-pilot, my issue is that my GH test stays Orange and never changes color to Green no matter how many drops of the reagent I add, tested twice and both times I stopped at around 25-30 drops because I knew there was something wrong and I did not want to waste the entire reagent.

Thank you.


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## hoppycalif (Apr 7, 2005)

I have had an API GH test kit quit working, presumably because it was beyond its shelf time limit. When I purchased a new one, it worked just a little better, so I replaced it with a Tetra kit and that one worked very well. I'm guessing that the indicator dyes used are not very stable.


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## ray-the-pilot (May 14, 2008)

Try the test using distilled water


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