Adding magnesium and calcium, how much? - The Planted Tank Forum
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post #1 of 7 (permalink) Old 01-30-2005, 03:46 AM Thread Starter
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Adding magnesium and calcium, how much?

I have a small problem.

First of all, this is our tapwater:
No chlorine or chloramine
pH 7.9
KMnO4 consumption(?) <2mg/l
Conductivity (25C) <20 mS/m
Carbonate hardness 2 dKH
Ammonium 0.01 mg/l
NO3 0,3-1 mg/l
NO2 <0.003 mg/l
Fe 0.03 mg/l
Mn 0.02 mg/l

Total hardness 3.8 dGH
Calcium hardness 2.5 dGH
Magnesium hardness 1.3 dGH

My problem is this. I have a 132 gallon (500 liters) tank and I am turning it to a closed paludarium with shrimps, apple snails, MTS and clams. Because of the apple snails, I need to raise the pH with baking soda to about 7-7.5 and raise the GH to about 8 to give them enough calcium. It will be heavily planted. What is the best way to raise the GH? If I'd add only calcium, the ratio would be Ca 6.7 and Mg 1.3 dGH. Not so good, right?

When adding them both, what would be a good ratio? Magnesium ? dGH + calcium ? dGH = total hardness 8 dGH

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post #2 of 7 (permalink) Old 01-31-2005, 09:28 PM
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You can add just calcium, your Mg is sufficient. Calcium carbonate will raise both Kh and Gh. The problem with Calcium carbonate is that it takes a while to dissolve. You can add it to your filter media or put some in the substrate if you don't want to be bothered adding calcium everytime you do a water change. The other option is to add calcium chloride for Gh and baking soda for Kh, but this would have to be done everytime you do a water change.

My water is actually softer than yours, I just simply added calcium carbonate to the substrate to increase Kh/Gh and I add about 10-15 ppm Mg at every waterchange to keep enough Mg for plants.

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post #3 of 7 (permalink) Old 01-31-2005, 10:35 PM Thread Starter
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Thank you for your answer

I've been using some crushed coral on the bottom of the small snail tank to keep the pH above 7 (since it doesn't dissolve much in pH over 7, I think it will start dissolving more if the pH crashes under 7, and so works as a sort of buffer) and added baking soda and gypsum, CaSO4. I just don't like the gypsum because of the sulfate it contains. I will be using potassium sulfate and maybe a bit magnesium sulfate (or do you think I don't need to add any Mg?) in the planted tank, so if I would add calsium sulfate too, there might be too much sulfates in the water.

Is there any (not too expensive) pure calcium source?

I think I should calculate a good recipe for my PMDD, I've been using the regular one mostly used here in Finland, but since I know what's in my water I could try to get the recipe as useful as possible. I use potassium and magnesium sulfate, chelated manganese and iron and Hortigrow Mikro containing: B 0.33 g/100 ml, Cu 0.05 g/100 ml, Fe 2.0 g/100 ml, Mn 1.14 g/100 ml, Mo 0.025 g/100 ml, Zn 0.3 g/100 ml. I also have potassium nitrate to add nitrates to the tank. And I do 50% water changes every week. I won't be using PMDD every week, but every three weeks. 1. week: PMDD, 2. week: Tropica Master Grow, 3. week: Seachem Flourish and Flourish Trace. I am thinking about doing this because I'd like to give the plants best care possible, and since all the fertilisers are a bit different, varying the type will give best results, right?

I will be doing some reading and update my knowledge about PMDD and check how you all dose it. But if someone has spare time, I would really appreciate help with that too

Last edited by rain-; 02-01-2005 at 01:02 AM.
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post #4 of 7 (permalink) Old 02-01-2005, 02:13 AM
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Originally Posted by rain-

Is there any (not too expensive) pure calcium source?

Pure (elemental) calcium reacts violently with water - producing hydrogen gas and calcium hydroxide! Try calcium chloride if you want something that is fairly soluble. Otherwise you have the other two options you mentioned - calcium carbonate and calcium sulfate.



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post #5 of 7 (permalink) Old 02-01-2005, 08:37 AM
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50 lbs of crushed oyster shell for poultry will cost your around $7. I have seen some feed stores do up 1 lb bags. It will dissolve eventually. I have seen bridgesi snails rasping on bits of the shell as well.

A cuttle bone for caged birds will do the same thing. Crushes easy in your hand.
Cheap generic calcium supplements for people is usually just calcium carbonate.
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post #6 of 7 (permalink) Old 02-01-2005, 02:00 PM Thread Starter
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KevinC: Oh, I didn't know that about pure calcium. I'm not that good with chemistry. So it really is good that I am asking this here instead of making a fool out of myself in local pharmacy. Thank you for explaining it to me.

Would the chloride in CaCl2 harm plants if I am adding it to the tank as much as to raise total hardness for 4dGH in 79 gallons?

SueNH: I have found only crushed limestone for chickens here and it contained some fixed residue (ash) and I don't think it's pure enough to put in the tank with fragile invertebrates

I think the easiest thing for me to do is buy coral sand and put 1/4 of that and 3/4 of sandblasting sand as the bottom substrate. But I will keep it as a backup thing only and I'd like to add something easily measured and soluble to the water every water change.

CaCl2 sounds really fascinating since it is the most soluble of those. Has some of you used it in planted tanks?
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post #7 of 7 (permalink) Old 02-03-2005, 11:46 PM
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Yes, I am using CaCl2 after running out of CaCO3in my 100gallon tank. I bought it as Ice Melts. The strange thing about CaCO3 was, I could not measure noticeble GH increase even after the water cleared up. With CaCl2, I see big change quickly.

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