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Reducing Nitrate


parrdog

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G'Day All,

I have a 5ft tank that is run by two canister filters(1200l/h,860l/h) and a power head(2000l/h). Currently my tank inhabitants are mixed Malawi, Tangs, 2 Pictus Cats and a Pleco. I plan on changing over to Tropheus only and therefore have been keeping a closer eye on nitrates lately. My nitrate level at the moment is 30-40 mg/l. I recently decreased the amount of gravel in my tank. After I did this I noticed that my nitrate level didn't really change. I was told recently that I needed to change the bio material in my filter (Matrix porous rock) because it was over 12 months old and it would be clogged. Today I changed over half of the Matrix so as to not disturb bac colonies. I will change the other half in a couple of weeks. I am hoping that this will see the N levels decrease. I currently do weekly water changes of 30%. Has anyone got tips for me to maintain my nitrates at below 20mg/l without decking out my tank in plants? I have noticed that my 3 cats leave alot of waste. Could this be a contributing factor? I am sorry this is such a long query but some help would be extremely appreciated.

Thankyou in advance,

Jamie.

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As you know, waste products ultimately become nitrates. So yes, having "messy" fish will be a contributing factor to the nitrate level.

Changing gravel/filter media etc will have no effect on nitrate levels. As these things do not remove nitrate. What does? As you have alluded to - plant life. But since you dont want to be planting the tank, larger, more frequent water changes are your best course of action.

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I'm with ducksta. I think you better put duckweed, val, or anubias in your tank to reduce the nitrate. Otherwise do regular water changes. The other problem is it could be that your filter is not ready yet, so that it always converting the amonia and nitrite to nitrate. What is your ammonia and nitrite level in that tank?

Regards,

Fishly

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Unfortunately a few plants in a rift lake tank do little to reduce nitrates. An external sump and an emergent plant with a light above it may give significant results. Search "plenum" in google and have a look at what you find, it may help.

Craig.

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After the talk at the NSWCS by Andrew I ended up putting plenums in 2 of my tanks. *says to self, must get a nitrate tester*

Dave (YeW) suggested a biological nitrate remover made of a long (a few metres) piece of narrow black tube that a the water flows through and back into the tank at a drip rate, I thought that was a good idea.

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Hi Guys -

I still think coil denitrators will work better than plenum systems - this is simply because water is forced through the coil but must passively diffuse through a plenum.

I use plenums in a box. Essentially a 6" high tuppaware container with a plenum in. These seem to work quite well. This conclusion, however, comes from some rather poor evidence.

1. bubbles in the bottom/gravel layers of the plenum. So their is some kind of gas being produced.

2. this gas doesnt smell - so it is either CO2 or N2 (or something I havent thought of).

3. I cant detect any nitrates in my tanks using my Hagen nitrate kit - but my tanks are quite lightly stocked.

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I agree that water changes are the most effective way to reduce nitrates in the aquarium. There are two products available here that I have tried....Algone (from Biotec) and Nitra-zorb (by Aquarium Pharmaceuticals). Both work out to be rather expensive, especially in large volumed aquariums, however you can re-charge the Nitra-zorb. I find that water changes are the cheaper and more effective way to go. I have not tried the plenum system and will research this for my own interest.

merjo

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Not sure if others got your connection between Matrix and nitrate reduction. But in case others are not aware, Matrix is sold as having an impact on nitrate levels due to having a larger particle size. The information is that the outer layer is colonised by aerobic bacteria, and the inner core is able to support anaerobic due to the outer surface stripping it of oxygen.

It would be my thought that you do not need to replace the Matrix, as I feel that is just a way of the shops getting you to spend more money (I know, I’m a sceptic), but washing it in water from the aquarium will remove a lot of the dirt.

I also wonder, if the outer layer is getting a bit dirty, which will slow down the water flow through the Matrix, won’t that mean the area able to be colonised by the anaerobic bacteria will be increased? Wouldn’t this in turn be beneficial to reducing nitrate?

There is another product by SeaChem called Denitrate. It is a biological media, but a very small particle size, similarly sized as kitty litter. The idea is to pack it in a canister (closed container), and have a reduced water flow through it. I have done this, and in fact have the water going through a prefilter, with efisubstate (excuse spelling) along with mechanical filtration, which will help to reduce the oxygen content before going through my denitate filter. My Tropheus tank does not have nitrate, so unless my test kit is faulty (always a possibility unsure.gif ), the denitrate works rolleyes.gif .

Craig

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