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Nitrate Reduction Filter

DaveyG

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5 Mar 2014
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Hi
I have recently purchased a Nitrate Reduction Filter. My tap water Nitrate levels are between 30-40 ppm and I have been doing daily water changes equating to about 50% of the volume per week In my 270 litre tank.
The level of Nitrate in the tank is the same as the tap water so I intended to reduce it to below 20 ppm.
The tank is heavily planted so I am assuming that it would be useful to leave a level of Nitrate in the water for the plants.
 

ian_m

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The tank is heavily planted so I am assuming that it would be useful to leave a level of Nitrate in the water for the plants.
Yes use water as is and just dose fertilisers as normal. 99.999% or people who miss-measure their tap water using hobby grade test kits and then alter their fertiliser dosing usually run into plant health issues.

Why do you want to lower nitrate to 20ppm ?

Where are you getting your 30-40ppm level reading from ? I hope not a test kit !!!. What does your water board quote ?
 

dw1305

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Hi all,
I have recently purchased a Nitrate Reduction Filter. My tap water Nitrate levels are between 30-40 ppm and I have been doing daily water changes equating to about 50% of the volume per week In my 270 litre tank. The level of Nitrate in the tank is the same as the tap water so I intended to reduce it to below 20 ppm. The tank is heavily planted so I am assuming that it would be useful to leave a level of Nitrate in the water for the plants.
You don't need the nitrate reduction filter, if you are heavily planted the plants will naturally convert the nitrate to plant material.

If you have a floating plant (non CO2 limited) you can use its growth and leaf colour as a proxy of the nutrient content of your water. I called it the <"Duckweed Index">.

Most aquarium literature and forums etc vastly under-estimates the ability of plant/microbe systems to deplete all forms of fixed nitrogen.

Are the NO3 figures from your water supplier? You easily could have 40ppm NO3 at some points of the year if you receive Anglian Water etc., but <"nitrate test kits are fairly unreliable">. Because all nitrate compounds are soluble you have to reduce the NO3 to NO2 to get a coloured insoluble compound that you can measure color metrically.

cheers Darrel
 

DaveyG

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The figure I quoted for Nitrate levels in my tank were from my local water supplier. The stated figures are between 33-38 ppm. I used an API Nitrate test kit and that indicated the same value (40 ppm) both in the tank and from the tap.
I assumed this would be the case due to the frequency of my water changes.
I would prefer this to be lower as this will benefit the livestock.
This is why I decided to use the Nitrate reduction filter as a means of doing this.
 

dw1305

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Hi all,
I would prefer this to be lower as this will benefit the livestock.
This is why I decided to use the Nitrate reduction filter as a means of doing this.
That makes sense.

Can we have a photo of the tank? It doesn't need to be a whole tank shot, just the plants and ideally Amazon Frogbit if you have some?

cheers Darrel
 

DaveyG

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Here are some pictures of the tank. As you can see there is a Nymphae Lotus in the tank which I regularly cut back to allow light to the other plants in the tank.
 

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dw1305

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Hi all,
As you can see there is a Nymphae Lotus in the tank which I regularly cut back to allow light to the other plants in the tank.
The plants looks really healthy, it must be all the NO3. A plant like Nymphae is ideal. It has roots that improve the <"oxygenation of the substrate"> and also leak sugars etc that produce a rhizosphere with fluctuating REDOX values. The floating leaves aren't CO2 limited, meaning that it can convert a lot of the fixed nitrogen into plant material.

The fish look good as well. Assuming you don't have any fish issues? I don't see any reason for not just continuing without the filter. Silly question, but could you <"use rain-water"> for some of your water changes? If you can that would be a low NO3 water source.

A lot of the literature about harmful nitrate levels <"comes from non-planted tanks">, where NO3 is the "smoking gun" of previous high levels of ammonia and nitrite. When you add NO3, either from a salt (like KNO3) or where the ammonia and nitrite have already been converted to nitrate by microbial action (usually in waste water treatment) you need pretty high levels before it has an adverse effect on fish health.

Edit: I should also have said if the nitrate filter is an ion exchange resin you can regenerate it with KCl (rather than NaCl). The cation isn't relevant, but potassium is a lot better for a planted aquarium when compared to sodium.

cheers Darrel
 

DaveyG

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Hi all
Thank you for your feedback. As I already have the Nitrate reduction filter I will use it to provide a 50/50 mix of tap/filtered water. This mix should approximate to a Nitrate level of 20 ppm. This would gradually reduce the level of Nitrate in the tank over the course of a few weeks.
Living in a City I decided against using rainwater as it may contain too many pollutants.
 

dw1305

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Hi all,
As I already have the Nitrate reduction filter I will use it to provide a 50/50 mix of tap/filtered water. This mix should approximate to a Nitrate level of 20 ppm. This would gradually reduce the level of Nitrate in the tank over the course of a few weeks.
That should work.
Living in a City I decided against using rainwater as it may contain too many pollutants.
If you have the potential to collect rain-water? You can use a simple bio-assay technique to monitor your rain water quality. It is based on the <"Daphnia bio-assay">, which is widely used in water testing.
I seed the water butts with Daphnia and then when I draw the water off, basically if it has Daphnia present I know it is OK to use
You are probably OK, due to the demise of most of our industry, rain-water quality in towns is now quite good, you are possibly in most danger if you live in an area with lots of agriculture (via pesticide spray drift).

cheers Darrel
 
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