# Filtration in a NPT



## Bardus71 (Sep 29, 2011)

Please excuse the pun, but I would like use this thread to go fishing for your opinions on using filtration in a NPT, & who is practicing what.

My own situation is that I have a Fluval4 on my 4' NPT with the idea that the simpler the better. Let the soil chemistry & plant filtration do the work. My wife however wants a 'tidy' tank & I have had to reduce the amount of foliage on the plants. The result was expectable, more nutrients in the water column, duckweed bloom, messy tank. I was thinking an Eheim 2213 may help the cause here.

This is my first post here by the way, "Hi from Newcastle Australia".

My tank specs:
Sub: Capped potting mix & soil
Lighting: 2.2 WPG T8's, photoperiod 13hrs/day
Plants: 
Marsilea hirsuita
Lilaeopsis brisbanica
Hygrophila polysperma 
sunset hygro
Filligree Milfoil
Ludwigia repens
Scarlet Ludwigia
Ludwigia glandulosa
Blyxa Japonica
Pogostemon stellatus

Stock:
Blackworms in substrate
Various snails
RCS
2 corys
8 Glass Cats
5 small Angelfish (will reduce to 1 breeding pair when adults)
(to come)
12 Rummy nose tetras
12 Kuhli Loaches
12 Pygmy Corys


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## Michael (Jul 20, 2010)

Hi again!

I am a great fan of the Walstad method, but I am persuaded that good circulation is extremely helpful. On my 40 gal I use an Eheim 2217 (about 250 gph) and a powerhead (also about 250 gph). Filter output, intake, and powerhead are located to create a circular pattern of flow in the tank.

In the Eheim, the only filter medium I use is lava rock. There is a coarse sponge over the intake to keep large debris (and shrimp!) out of the filter. I am mostly interested in the Eheim for circulation, and secondarily for back-up biofiltration to keep the tank stable in case of an accident.

I want 10 X the volume of the tank to be circulated every hour. You can read a journal here: http://www.aquaticplantcentral.com/...uatic-plant-club/77266-journal-tributary.html

So those are my thoughts on filtration in an NPT. Duckweed is a messy pain in the neck, but the sudden growth you saw may have prevented an algae bloom. You might try taking out the duckweed, and using a larger floating plant that is easier to control. Amazon frogbit and red root floater are my favorites.

--Michael


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## Bardus71 (Sep 29, 2011)

Hey Michael, 

thanks for the quick reply! I checked your link & will get to reading through it when I get the time. Looks good. 1 immediate question, why lava rock specifically? I have some carbonite at home that looks like it has just come out of a molten guyser, is that the same? 

Cheers, 
Bardus.


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## Michael (Jul 20, 2010)

I used lava rock because it was easily available in the size I wanted (0.75-1"), it has a huge surface area for biofilm, and it is chemically inert. I'm not familiar with carbonite, but if it has similar characteristics it should be fine.


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## Bardus71 (Sep 29, 2011)

By the way, is there any chance of developing plant deficiencies if overfiltration occurs? For example, if I get a Eheim 2213 or 2215 and add purigen to polish the water, will it outcompete the plants for nutrients?


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## Michael (Jul 20, 2010)

In an NPT, we want the nutrients in the substrate, not the water column. This is why we use soil and other media that have high CEC. These absorb nutrients from the water, fish waste, etc. and release them to plant roots. So we are less likely to "over-filter" this kind of tank than a tank with an inert substrate and water column fertilization.

I don't know anything about Purigen except what SeaChem says on their web site. I have heard of people using it to remove tanins from NPTs, and it might be good for that purpose. But I don't think it would good to keep it in the filter all the time. Put it in for a short time to accomplish a specific change, then take it out.


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## mthom211 (Sep 3, 2010)

Hey Bardus!

Over filtration won't cause a deficiancy if you arn't using chemical filtration. All the same nutrients are there (well actually some N is gassed off but that's not too important) just in a different form. The plants just need to use more energy to use the nutrients.

I'm pretty sure plants prefer to take up K from the water column so if purigen (or macrophore that one of the sponsers on AL sell, it's cheaper and easier to recharge) removes K I wouldn't use it, not much K is added through fish food and tanks can easily become deficiant in K and this would speed up that process. We are constantly removing K through trimmings and adding very little of it back. It's not very sustainable I'm sure there's some permaculture could help come up with a solution, best I've thought off is burrying the trimmings in the substrate. Bit of a tangent lol

I can't remember if I sent you blyxa and frogbit... Blyxa is a great deep rooted stem that grows really fast and looks best dense so your wife might prefer that, once mine recovers after me going on holidays I can send some down. If your wife doesn't like lots of stems I doubt she would like frogbit roots but I've found it's great at removing waste. You could also stick a willow branch in or some pothos vines, that would be more environmentally friendly than upgrading the filter. Diana talks about using emerrsed plants to use wastes in the chapter "the arial advantage" in her book. 

Oh, just realised my username is different here, it's Matt here  not some stalker


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## aquabillpers (Apr 13, 2006)

My two thoughts:

First, the limiting factor in NPT's is CO2. A lot of water movement will drive off that limited CO2, starving the plants. Water circulation, if necessary, can be provided with a small HOB filter, adjusted to minimize surface disturbance. Many NPT people don't bother with it. High filtration is not compatible with the NPT concept.

Second, NPT's need nutrients in both the substrate and the water column. Not all plants are rooted, and even the rooted ones utilize what is in the water column.

Don't make growing aquatic plants more complicated than it has to be.

Bill


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