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No Filtration Tanks


  1. Need for filtration in planted tanks
    by David Aiken <d.aiken/> (Sat, 15 Feb 97)
  2. filterless tanks
    by "Roger S. Miller" <rgrmill/> (Sat, 23 Jan 1999)
  3. Filterless planted tanks
    by krandall/ (Sun, 24 Jan 1999)
  4. Filtration
    by krandall/ (Fri, 26 Feb 1999)
  5. More on Filter less Plant Tanks
    by George Booth <booth/> (Sat, 27 Feb 1999)
  6. lightly filtered tank question
    by "Roger S. Miller" <rgrmill/> (Mon, 10 Jan 2000)

Need for filtration in planted tanks

by David Aiken <d.aiken/>
Date: Sat, 15 Feb 97

On 13 Feb 1997, Jan Fidrmuc <> wrote:

>While reading Steve's instructions on growing Ellodea, I had a few 
>thoughts about need for filtration in heavily planted tanks. In 
>particular, it seems to me that filtration may not always be such a 
>good  thing after all. According to my understanding of the N-cycle, 
>fish produce predominantly ammonia --- which is also what the plants 
>prefer. A biological filter then  forces the bacteria to compete for 
>ammonia with the plants, which is not a good thing. So it seems to me 
>that it is better to leave it up to the plants to remove the ammonia and 
>only remove the nitrates with water changes.

Around 15 months ago, in a bid to get my nitrate levels down, I decided 
to steal a leaf from the reef tank crowd and instal a plenum in my tank. 
I don't have any marine tanks but I've always enjoyed Julian Sprung's 
reef notes in FAMA, as well as some of his nasty humour (g), so I bought 
a copy of "The Reef Aquarium" especially for the sections on filtration, 
lighting, and general tank management. I also bought Adey and Loveland's 
"Dynamic Aquaria" for its systems approach though I didn't want to use 
algae scrubbers and I figured they're probably redundant with enough 
higher plants in the tank. I'm definitely the only person I know who 
deliberately set out to start trying to run a plant tank on reef tank 
principles, and I did it because I wasn't happy with much of the material 
in "The Optimum Aquarium". I don't know whether it's just the poor 
quality of the translation but I find it confusing and frequently 
inconsistent. It also didn't give me a grasp of the principles. Just like 
many people on this list like to know what's in their fertilisers, I'd 
like to have some understanding of the biological processes and 
interactions going on in my tank. I'm prepared to say right now that I 
think "The Reef Aquarium" is a better book for planted tanks than "The 
Optimum Aquarium"! I definitely learnt much more in the way of basic 
biological principles that I could apply from Julian Sprung and Charles 
Delbeek's book (and the pictures were better too - don't quite match 
Amano's but that could just be that they have poorer taste in subject 
matter ;-) )!

I rebuilt my 3 ft tank with a UG plate and no uplift tubes, filled it 
with RO water prepared with Kent R/O Right, and reinstalled my filter - 
an internal Eheim sponge filter. At startup nitrates were predictably 
zero and rose gradually. I was surprised to find after 9 months, however, 
that they were up around the 25 ppm level when measured with Dupla's 
nitrate kit. The plenum didn't seem to be working the way I'd hoped. I 
proceeded to bring them down with massive water changes and eventually 
got back around the 4 to 5 ppm mark. That also cut my mild phosphate 

I then decided to bite the bullet and remove my "nitrate farm" - the 
filter sponge. I retained the powerhead for water circulation, and 
eventually added a second smaller power head.

Lighting is 2 Corallife full spectrum daylight tubes (changed from 2 
tritons). They're mounted about 8 inches above the open tank top, and I 
have the mylar film I mentioned in an earlier posting stuck inside the 
reflector housings using double-sided tape. I'd like to use cheaper tubes 
like commercial triphoshor cool whites but I can't find them here in 
Brisbane in 3 foot lengths. Nobody will do an order for 2 or 3 tubes 
either - not a big enough quantity. I'd prefer to add another tube or 
two, or swap to MH lamps, to increase my lighting levels but money is an 
issue at present. I'm using the small Dupla CO2 set up without any 
electronic controllers - just a bubble every 2 or 3 seconds in the bubble 
counter. I don't switch it off at night.

I scrupulously conducted ammonia, nitrite, and nitrate tests weekly for 
several months. Ammonia usually shows a very slight trace of colour on 
whatever test I use - above zero and below the first reading level. 
Definitely not a worry. Nitrite is always zero. Nitrates are holding at 
around the 2 ppm level. pH is around 6.6 to 6.8 and the water is soft at 
around 2 to 3 degrees KH and GH. I've stopped testing weekly and now test 
only every 3 to 4 weeks.

I had some fish deaths around the 1-2 month mark, but this was also 
Christmas/January height of summer in the southern hemisphere. I 
sometimes get tank temperatures of around 32 degrees C at this time of 
year if I leave the tank covered (the heater never switches on when its 
like this and I actually used to remove it from the tank at one time). 
It's always a rough period for my fish and I think that was the issue 

My fish load is now lower than it has ever been in the tank, though I 
would never have regarded it as being really high. Currently I have 9 
cardinal tetras, 3 or 4 pygmy Corydoras, 4 bronze Corydoras, and 3 
otocinclus. The tank is also more heavily planted than ever, and I keep 
adding more. i'm finding I'd rather add a plant than a fish (a big 
change!). I'm getting my algae problems under control and part of the 
reason there came from lurking on this list for several months - I 
increased my fertiliser dose since reducing it to zero hadn't helped! 
Another leap of faith - removing the biological filtration does not seem 
like a sound thing to do, neither does feeding nutrients to the tank if 
you have algae, but both have been highly positive steps for me. I also 
doubled my plant load.

My tank looks the best it has ever looked, and I'm actually relying on 
tank appearance rather than test results to guide me as to what I do. My 
java fern keeps producing adventitious plants at the leaf tips. I have an 
aponogeton (Ulvaceous ?) that keeps throwing flower spikes, the 
hygrophila keeps getting cut back, and my echinodorus are staying healthy 
and not succumbing to algae. Everything looks GREEN - it's a lovely 
colour! I'd like to reproduce Amano's "lawn effect" but I think I'd need 
a lot more lighting to succeed.

The tank seems quite stable as far as test results go, and I've stopped 
worrying about whether the whole experiment is going to crash.

I've noted a few comments in this Digest from some people like Karen 
Randell mentioning success with unfiltered tanks. At the stage I tried 
this, I had heard no comments about the possibility of successfully 
running an unfiltered plant tank and I was really into "risking" to see 
if I could control my slowly climbing nitrate level and solve my algae 
problem. I was encouraged by what I had read of reef tanks running 
successfully without "technological" biological filters - biological 
filtration does occur in the live rock as I suspect it also does in my 
substrate, and in and on my plants. I'm satisfied that it can work quite 
well in a plant tank. I have to admit to more than a little pride that I 
seem to be getting better results than a lot of people while breaking all 
the "accepted" rules and removing the filter.

I'm also finding the lower fish load attractive. At first I missed the 
larger number of fish. With the smaller numbers, the ones you see seem 
more interesting. They're all looking healthier (or is that the colour 
contrast with all that lovely green I now have), and they seem to act 
more natural or more relaxed with less crowding. Reef tanks also run with 
low fish loads, and I'm beginning to think that things really are 
healthier that way.

I've set up a second tank (a 2 foot) near a window with a small power 
head, some hygrophila and some java fern, and a pair of rams I took out 
of the 3 foot because they were aggressive. I'm relying on natural 
morning light through the window. Everything's going fine though I get a 
little smear algae on the tank walls. I should get around to upping the 
plant load the next time I prune the 3 foot.

I'd be really interested to hear some hints and comments about experience 
with unfiltered tanks from people like Karen and anyone else who has 
tried this approach. I'd really like to see a good book come out on 
planted tanks which looks at management techniques including this kind of 
natural tank approach, and which explains some of the biological workings 
of a planted tank. In fact, the contents schema for Vol.1 of "The Reef 
Aquarium" would be just about ideal from my point of view - some material 
on the natural environment, filtration techniques, nutrient control and 
supplementation, lighting, water movement, layout and design including 
the use of wood and rocks, and plants. You really couldn't beat it (this 
is a quite shameless hint/plea!). Maybe a book from members of the AGA  
with different chapters by different authors - there really does seem to 
be enough expertise on this List to fill the need. I hope Julian Sprung 
and Charles Delbeek don't try to sue for plagiarism if someone takes me 
up on this suggestion, but this is the kind of plagiarism that would be 
quite the sincerest form of flattery.

A parallel book, or a set of appendices, on DIY technology in the 
lighting/ CO2/ fertiliser area would really just top it off.

David Aiken

filterless tanks

by "Roger S. Miller" <rgrmill/>
Date: Sat, 23 Jan 1999

On Sat, 23 Jan 1999, Ed wrote:


> This brings up a concern for me, if the
> plants does a better job of filtration than conventional filters does
> this mean that filters are NOT needed on a planted tank?

Filters are not needed in a planted tank.

Well, not for the sake of the plants, anyway.  If you want to keep a heavy
fish load, then maybe you want a biological filter in addition to the
plants.  In either case, you still need to provide circulation.

To expand on this a little...  I think that a large part of the nitrogen
content in fish foods - including high quality prepared diets and live
food - is in compounds that aren't readily broken down to give
plant-available nitrogen.  I suspect (but can't prove) that most of the
phosphorus is quickly released to the water.

In a filtered tank the detritus containing the relatively refractory
nitrogen is removed and that may push the nitrogen:phosphorus ratio down.  
In an unfiltered planted tank the detritus stays in the tank (it usually
settles out in thick stands of plants) and that gives extra time for fish,
snails and bacteria to convert it to plant available forms.  That results
in a higher nitrogen:phosphorus ratio.

The upshot is that if you don't use filtration you might not need to add
nitrate to make phosphorus the growth-limiting nutrient.

Geez, ss that obtuse enough?

Running a tank without a biological filter is I think an exercise for
experienced aquarists.

Roger Miller

Filterless planted tanks

by krandall/
Date: Sun, 24 Jan 1999

>>From the looks of this test it would seem to me that the filter was
>robbing the plants of needed nutrients and converting it into nitrates,
>I may be wrong on this note.  This brings up a concern for me, if the
>plants does a better job of filtration than conventional filters does
>this mean that filters are NOT needed on a planted tank?

This is another subject that comes up again and again.

If you keep are light-moderately stocked well planted aquarium, you do not
need much if any _bacterial_ filtration.  If you have a high enough
stocking level that nitrate tends to build in the tank, then you probably
need the back up of bacterial filtration for the safety of your fish.  

Water motion is a good thing in a planted tank, so most of us choose to run
either powerheads (which need to have a sponge attached to keep from
clogging) or some type of filter with minimal bacterial action to keep the
water moving.  Some people do fine without even this.

Most of us also prefer to have some form of mechanical filtration to remove
suspended particles from the water.  Again, this is optional, not strictly

So decide what you want to accomplish, and choose a filtration method that
will do those things, and no more.

Karen Randall
Aquatic Gardeners Association


by krandall/
Date: Fri, 26 Feb 1999

Dave Gomberg wrote:

>Since there seem to be so many filtration advocates on this list I have
>some questions:
>In a tank with lots of plants and
>1.  no animals, is filtration useful?
>2.  very few animals, is filtration useful?
>3.  moderate animals, is filtration useful?
>4.  In case 3, what role does filtration play?  What objectives does it
>accomplish?  What bad would happen if you omitted it?

I can give you some anecdotal information.  I have twice in the course of
years turned off a filter for cleaning, on heavily planted, moderately
stocked tanks and forgotten to turn them back on after they werte replaced.
 I haven't noticed my error for as long as 8 weeks after the filter was
turned off. (What can I say, I'm lazy about cleaning filters<g>)
Absolutely _NOTHING_ positive or negative has happened to the tanks during
these periods.  The plants have continued growing, the fish have continued
swimming, and yes, even spawning.<g>  The water has remained clear, and if
there was more mulm on the bottom than usual, it wasn't enough more that I

I still use some form of filtration on my tanks because I think that
circulation _is_ important, and if you don't use a filter, you have to
devise a method of keeping powerheads from becoming clogged (i.e.
filtration)  But I don't worry much about what type of filtration.  I think
that if you have little enough nitrate that you need to supplement,
filtration is probably if little concern.  If you have to change water to
keep nitrate levels down, you are probably relying pretty heavily on
bacterial filtration, and removing it could cause problems.


More on Filter less Plant Tanks

by George Booth <booth/>
Date: Sat, 27 Feb 1999

>Date: Fri, 26 Feb 1999 13:54:37 -0500
>From: "James Purchase" <>
>This last bit I don't understand totally - if all of the nitrogen input is
>in the form of NH3 or NH4+, and is used by the plants for growth, there
>should be no build-up of nitrate. 

The problem is that the concept was grossly oversimplified. The assumption
is that nitrifying bacteria are only in the filter - "no filter, no
nitrifying bacteria". This is not correct. 

Nitrifying bacteria occur everywhere in an aquarium; on the gravel, on the
glass sides, on equipment, on plant leaves, even in the water. Biological
filters are useful in that the biomedia provides for a higher concentration
per volume of bacteria. 

Dr. Alfred Gianascol, in "Water Chemistry in Closed System Aquariums"
(1987), demonstrated that in a typical aquarium [without plants], the
actual filter only provided about 15% of the total nitrification. The
biofilm on the glass and gravel provided the rest.

So, you can safely assume that there are in fact huge numbers of nitrifying
bacteria in even the most densely planted tank and that they will happily
convert any ammonia/ammonium that drifts their way into nitrate. They DO
compete with the plants for nitrogen and WILL generate nitrate. 

I conjecture that tanks with very low nitrates have some form of
denitrification going on - either the plants are not getting their fill of
ammonium and are utilizing nitrate or denitrifying bacteria are at work (or
George Booth, Ft. Collins, Colorado 

lightly filtered tank question

by "Roger S. Miller" <rgrmill/>
Date: Mon, 10 Jan 2000

On Mon, 10 Jan 2000, Amy Hembree wrote:

> I'm in the process of buying a 125-gal. tank from my LFS. When I told
> the guy I planned to heavily plant it and stock it with loads of
> rummynoses, he said that while it definitely needed substrate heating,
> it didn't need any filtration.

Get the substrate heaters if you already have everything else you want and
you still have money to burn.  Their benefit to the aquarium is arguable
(in fact, there's lots of argument about that in the archives of this
list) but I think even the proponents of undergravel heating agree that
there are more effective ways to spend your money (adequate light and a
dependable CO2 system come to mind).

I think filterless tanks are great.  There are two things to keep in mind.
First, your plants need good water circulation -- they can't move around
to get water-borne nutrients so the nutrients have to go to them -- so
even if you don't have a big filter you still need something that will
provide good circulation.  I use powerheads.  Second, you should probably
build up the fish population in an unfiltered tank fairly slowly.  That
way you can be sure that the plants are established, growing well and able
to consume the wastes that the fish are producing.

Roger Miller

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