nitrate ferts bad for fish? - The Planted Tank Forum
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post #1 of 5 (permalink) Old 01-19-2008, 08:29 PM Thread Starter
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nitrate ferts bad for fish?

I've always heard that nitrates above 20 ppm are bad for fish. Can't this easily happen with the EI method? I'm also confused about the Flourish nitrate. It says that it adds a different nitrate source that won't show up on my test kit reading. So if my nitrates read 20 ppm after dosing with that, does that mean my nitrates (the kind the traditional test kits measure) are really only 10ppm? What is the difference b/w the 2 types of nitrate and is one less harmful to fish? I have dry ferts ordered. Maybe that will simplify it.
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post #2 of 5 (permalink) Old 01-19-2008, 11:40 PM
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I don't know if 20ppm is the right number, but you shouldn't really have a huge issue with EI. I am guessing the test kit measures one compound containing nitrate, and won't pick up the other compound. (i.e. Ammonium Nitrate versus Potassium Nitrate) I could be wrong though. As long as you don't overdose anything, it shouldn't hurt your fish.

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post #3 of 5 (permalink) Old 01-20-2008, 12:46 AM
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You have to remember that with EI, you are doing 50% weekly water changes per week to remove any excess amounts and reset the tank that combined with the fact that your plants will continually utilize nitrate to grow assuming all other things are equal - you have a heavily planted tank, your are dosing other required nutrients(the EI method pretty much assures this) your c02 is within appropriate levels, and your lighting is sufficient combined with your c02 level to spur nitrate uptake and growth, you should be fine. From what I understand, even the Father of EI, Tom Barr maintains several tanks with what would be considered high nitrate levels and he has kept fish in those tanks for several years without problems. Getting accurate nitrate level readings is also dependent on ensuring that you are using accurate properly calibrated test kits. It is not a bad idea to test your tap water with such a kit as some tap water can contain significant nitrates. In cases where your tap water is high in phosphates or nitrates you can cut back on the amount that you dose with EI. EI is a highly flexible method and many people successfully adapt it to their particular tap water parameters without problems.

I think that high nitrates only become an issue in non-planted tanks where they don't end up being used and will often build up and remain at consistently high levels, especially when people over feed their fish, don't do water changes, and overstock their tanks full of fish.

One thing that helps soak up nitrates like a sponge is the use of floating plants like egera densa, cardamine lyrata, water lettuce, riccia, etc., So if high nitrates concerns you, having some floating plants to soak up extra nitrates is not a bad idea.
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post #4 of 5 (permalink) Old 01-20-2008, 12:53 AM
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The idea that low levels of nitrate 20 ppm and under are harmful for fish is because in a normal aquarium the ONLY way to get those levels is through the nitrate cycle. It's the ammonia, nitrite and other DOC that accompany the nitrate levels that actually harm the fish at those levels.

If you are dumping in KNO3 then you don't have the other by-products.
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post #5 of 5 (permalink) Old 01-20-2008, 04:18 AM Thread Starter
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I see. I won't worry so much about it then. Thanks.
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