Do high tech planted tanks reduce GH fast? - The Planted Tank Forum
 
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post #1 of 13 (permalink) Old 06-01-2014, 06:15 PM Thread Starter
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Do high tech planted tanks reduce GH fast?

Let's say you have a heavily planted high tech tank, and you don't do water changes for at least 3 weeks, will the plants reduce the GH in your water? My understanding is that GH is what measures calcium and magnesium. I am fairly new to planted tanks, so I hope I'm not asking an ignorant question.

Last edited by lauraleellbp; 06-02-2014 at 06:04 AM. Reason: spelling
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post #2 of 13 (permalink) Old 06-02-2014, 05:44 AM
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It isn't an ignorant question. It is one that needs to be discussed periodically. Plants use calcium and magnesium, but those are not used in such large quantities that depleting the GH will be a problem, except possibly for very low GH tanks. I don't recall seeing anyone report a problem caused by such depletion of the typical GH range water we use. However, not all well water contains adequate magnesium, so it can be possible to be short on magnesium, whether the plants use it up or not. Checking your water company water quality report should show whether there is significant magnesium in the water.

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post #3 of 13 (permalink) Old 06-02-2014, 01:17 PM
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I agree completely with Hoppy. Plants do not use Ca and Mg very quickly at all. They are not really considered "macro" nutrients because they aren't used as much as NPK. I'd estimate only a few ppm a week are used up.
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post #4 of 13 (permalink) Old 06-02-2014, 04:23 PM
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I think ratio dry weights would suggest maybe 2 ppm of either, per week... would be at the high non limiting end.




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post #5 of 13 (permalink) Old 06-02-2014, 07:47 PM Thread Starter
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Thanks everyone for the reply. I bought a test kit to test the GH, and my tap water is at 14 GH. Someone advised me to used crushed coral or dolomite to increase the levels of magnesium and calcium on my dirted tank, but my GH is already high as it is. I will be gone to Australia for a month and I was worried about my medium/high light plant draining the calcium and magnesium too fast. With my Finnex Led fixture, at the substrate, I am getting about 46-48 par.

So I decided to look up the water quality report for my city and this is the information of my water below:
Calcium (ppm)
Average detected: 76
Range low-high: 46-99

Magnesium (ppm)
Average detected: 14.9
Range low-igh: 9.6-21



I have so many quesitons, and I think I will be asking more because I think that there are a lot of things that need to be addressed on the forum.


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Last edited by kidgrave; 06-02-2014 at 07:59 PM. Reason: added more info
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post #6 of 13 (permalink) Old 06-03-2014, 01:51 AM
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Quote:
Originally Posted by plantbrain View Post
I think ratio dry weights would suggest maybe 2 ppm of either, per week... would be at the high non limiting end.
I agree, I was thinking similar numbers.

I adapted the information in this chart to match generally accepted non limiting dosing ranges. The column on the far right is a good target dose for aquatic plants for each nutrient. Though some could be higher without ill effects.


From:http://www.aquaticplantcentral.com/f...tml#post666538
On a slightly different note. I think it is kind of an odd thing that we consider phosphorous a "macro" nutrient when the use of phosphorous is often well below the use of other nutrients like Ca & Mg.
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post #7 of 13 (permalink) Old 06-03-2014, 03:54 AM
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Your GH, both the Ca and the Mg portions are just fine for you to leave the tank for several weeks or a month. I sure would not add GH booster to that.
Enjoy your trip.

Quote:
On a slightly different note. I think it is kind of an odd thing that we consider phosphorous a "macro" nutrient when the use of phosphorous is often well below the use of other nutrients like Ca & Mg.
A lot of the way we think about fertilizer comes from plants growing on land, and soils might be short of Ca or Mg, but MUCH more often they are short of N, P, K, so these three are macros. Carbon is not even considered, since land plants are able to get their carbon from the air.
In the average aquarium the water is supplying the Ca and Mg in reasonable quantities, so again the N, P, K are the 'big 3'.
Actually, carbon ought to be on that chart, when you are trying to figure out aquatic plant nutrition.
Per Diana Walstad, Ecology of the Planted Aquarium, aquatic plants are about 40% carbon by dry weight, so that carbon is needed in amounts over 20 times the nitrogen requirement.
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post #8 of 13 (permalink) Old 06-03-2014, 04:32 AM
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Originally Posted by Diana View Post
Carbon is not even considered, since land plants are able to get their carbon from the air.
Very true. I've had a hell of a time finding enough papers describing CO2 deficiency. Someone recently sent me one on algae and CO2 depletion in lakes which was interesting, and I've read a few from before which describe carbon deficiency and toxicity in crop plants. Though carbon deficiency really doesn't seem to have been studied very much. If you find any relevant papers let me know!

I also just recently found out a way of testing the CO2 in our water with a fairly high level of accuracy. I need to flesh out the method a bit more and see if I can source the right materials so I do a bit of measuring and see how well it works.

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Originally Posted by Diana View Post
In the average aquarium the water is supplying the Ca and Mg in reasonable quantities, so again the N, P, K are the 'big 3'.
I'd say N, K and iron are the 3 most commonly deficient nutrients in our aquariums. I haven't seen too many phosphorous deficiencies in aquatic plants. I'd say it is actually one of the more rare deficiencies. Though that might just be because PO4 is introduced to the tank from fish food/waste at usually adequate levels and iron is pretty good at degrading and precipitating out of the water column becoming unavailable.

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Originally Posted by Diana View Post
Actually, carbon ought to be on that chart, when you are trying to figure out aquatic plant nutrition.
It should be, but again, nobody studies a lack of carbon so I don't have a strong reference value and I haven't run the tests I want yet.
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post #9 of 13 (permalink) Old 06-03-2014, 06:00 AM
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Quote:
Originally Posted by Zapins View Post
I agree, I was thinking similar numbers.

I adapted the information in this chart to match generally accepted non limiting dosing ranges. The column on the far right is a good target dose for aquatic plants for each nutrient. Though some could be higher without ill effects.


From:http://www.aquaticplantcentral.com/f...tml#post666538
On a slightly different note. I think it is kind of an odd thing that we consider phosphorous a "macro" nutrient when the use of phosphorous is often well below the use of other nutrients like Ca & Mg.
I think those ranges will be non limiting if maintained for any aquatic plant and should not pose any excess issues either.




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post #10 of 13 (permalink) Old 06-03-2014, 06:03 AM
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To study CO2 deficiency, take a nice example of a healthy aquatic submersed plant in a CO2 enriched system, then turn the CO2 down/off.

Pretty simple.

Measure stem elongation, dry weights etc, visual assessments, pics, video etc.
Measure CO2 carefully.
Particularly the 1st 3-4 hours of the light cycle.




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post #11 of 13 (permalink) Old 06-03-2014, 06:05 AM
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That isn't a deficiency though, that is a limitation.

The plant will still grow because it still has access to a low level of CO2 diffusing in from the atmosphere.

The only way to see a deficiency (total lack) is to deplete the water column of CO2.
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post #12 of 13 (permalink) Old 06-04-2014, 06:13 PM
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Quote:
Originally Posted by Zapins View Post
That isn't a deficiency though, that is a limitation.

The plant will still grow because it still has access to a low level of CO2 diffusing in from the atmosphere.

The only way to see a deficiency (total lack) is to deplete the water column of CO2.
This will actually happen in a heavily planted tank with high lightning towards the middle of the light cycle. If you take a pH probe and measure the co2 during the middle of the cycle it could rise by a half a point or so (with no co2 injection).

Make sure there is minimal surface movement for gas exchange.
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post #13 of 13 (permalink) Old 06-04-2014, 08:24 PM Thread Starter
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Quote:
Originally Posted by Diana View Post
Your GH, both the Ca and the Mg portions are just fine for you to leave the tank for several weeks or a month. I sure would not add GH booster to that.
Enjoy your trip.



A lot of the way we think about fertilizer comes from plants growing on land, and soils might be short of Ca or Mg, but MUCH more often they are short of N, P, K, so these three are macros. Carbon is not even considered, since land plants are able to get their carbon from the air.
In the average aquarium the water is supplying the Ca and Mg in reasonable quantities, so again the N, P, K are the 'big 3'.
Actually, carbon ought to be on that chart, when you are trying to figure out aquatic plant nutrition.
Per Diana Walstad, Ecology of the Planted Aquarium, aquatic plants are about 40% carbon by dry weight, so that carbon is needed in amounts over 20 times the nitrogen requirement.
Thank you so much, Diana, and I appreciate your information. I will be gone to Australia for a month, and I am giving my sister specific instructions of how to take care of both of my tanks. I told her that I would buy her shoes, and pay her really good money for making sure that my plants and fish survive. As far as soils go, which brands do you advise to use in a planted aquarium? I am wondering about other alternatives besides miracle gro organic mix potting mix because this soil has some mixed reviews online, and I would like to see if there is something out there of better quality.


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