How to tell if I need to dose macro-nutrients ? - The Planted Tank Forum
 
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post #1 of 6 (permalink) Old 07-26-2010, 08:48 AM Thread Starter
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How to tell if I need to dose macro-nutrients ?

I just setup a new 28G planted tank 4 days ago. Some bacteria have started forming on the filter media as I seeded it with my old filter gunk and new bacterial culture. I also have fish in the new tank (transferred from my old one). Started injecting CO2 about 32 hrs ago, and have dosed Seachem Flourish Comprehensive twice so far. Once on day 1, and once this morning. 2.5ml each time. I have also inserted fertilizers into the substrate.

CO2 levels are about 30ppm based on my drop checker. Lighting is 2.5WPG T5, 12 hrs per day. Plants that are not rooted in the substrate (i.e. planted on driftwood) have started shedding and melting leaves. One of them is an Anubias Nana, the other is some kind of pennywort.

Iíve read that this is normal with new plants Ė something about submerged and emerged growth? How long should I wait and see before taking action?

Iím also unsure about nitrates and phosphates. Some sources say that fish food and fish waste would provide sufficient macro nutrients for plants. In addition, there are also nitrates and phosphates in Flourish Comprehensive. How do I tell if I need to dose more nitrates and phosphates or if I need more light/CO2?
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post #2 of 6 (permalink) Old 07-26-2010, 09:15 AM
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I've just re-started my planted tank after a massive hair algae outbreak caused due to me mainly being a newbie. I look forward to some experienced aquarists chiming in.
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post #3 of 6 (permalink) Old 07-26-2010, 12:25 PM
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Hi redryder,
You probably do have less CO2 then you think. What do you use in your DC? Are you using 4dKH water and how are you getting the CO2 into the water column? A drop checker with 4 dKH and a green reading (+/- 0.2 degrees pH) says you have between 18.9 and 47.5ppm CO2. So, gradually adjust your CO2 up and wait a week or two. Something else to look at is how well the water is circulating. Water flow is very important too.

Flourish is not a great source for macro nutrients, (N, P, K, S, Ca and Mg) unless your levels are high to begin with. Your 2.5mL of Flourish adds about 0.02ppm N; 0.002 phosphate; 0.08ppm K+, and 0.07ppm of iron to your water column. Personally, I would bump the dose up to 5mL to raise the levels of iron and find another source for your macros.

What is it about nitrate and phosphate that's so scary? Boatloads of light and CO2 are what scare me. CO2 kills more fish then nitrate or phosphate ever will. And driving high levels of light is like driving a car at high speeds - more maintenance, energy and skill are needed. You are trying to run your (highlight/ CO2 injected) race car on regular gas. People that add nutrients from fish food, ride (low light/low tech) bicycles. It's a choice. You are risking low levels of NPK needlessly and adding more light would just make the situation worse.

Maybe some one else can explain without sounding so grumpy. My cat got me up early today and I don't mean to sound harsh. I hope this helps and good luck.


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post #4 of 6 (permalink) Old 07-26-2010, 04:41 PM
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2.5 watts per gallon of T5HO light is way more than enough light. If that tank is 18 inches high a single T5HO bulb, with a typical T5HO reflector, will give you high medium light, enough to grow anything. 2.5 x 28 = 70 watts. I don't know what bulbs you are using to get 70 watts. Two 39 watt bulbs would be 78 watts, two 24 watt bulbs would be 48 watts or 3 would be 72 watts - maybe that's what you have?

Given that you have very high light your plants cannot get enough of any of the nutrients unless you provide them. You need to dose nitrates, phosphates, potassium, trace elements. The easiest way to do that is to follow the EI dosing method, as described in https://www.plantedtank.net/forums/fe...tml#post190421

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post #5 of 6 (permalink) Old 07-27-2010, 12:47 AM
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Hi Hoppy,
As soon as Gerry gets his PAR meter out to me I'll be checking some guys 29 gallon tank with double T5's as well as a double T-8 walmart shop light with growlights over a 75 gallon tank and my 10 and 20gal.T. I'll be sure to share with the rest of the class.


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post #6 of 6 (permalink) Old 07-27-2010, 01:27 AM
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Quote:
Originally Posted by tug View Post
Hi Hoppy,
As soon as Gerry gets his PAR meter out to me I'll be checking some guys 29 gallon tank with double T5's as well as a double T-8 walmart shop light with growlights over a 75 gallon tank and my 10 and 20gal.T. I'll be sure to share with the rest of the class.
Be sure to include the distance from the PAR meter sensor to the light bulbs. It is hard to get such data, since most people just measure their own tank checking various places in the tank, with no data about what the distances are.

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