# Isn't the aquarium it self a filter?



## chagovatoloco (Nov 17, 2007)

I've been doing some thinking (something I really know nothing about). So when I think of a filter the goal is beneficial bacteria, Aside from removing partials. Moving water around surface area creates an environment for the bacteria to grow and nitrogen cycling breaks down fish waste. So if I have live growing plants and plenty of water movement can't I just turn the whole tank in to a filter? Especially with healthy plans I don't see why a filter is needed. I will admit that this thinking comes from doing a lot of reading on filterless reef tanks. Even with a fully stocked tank I can't see why a filter is needed. I know I am not the first to come up with this and I figure you guys know more than me. So can my aquarium be the filter? 

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## Yo-han (Oct 15, 2010)

This is true! A fully grown tank with a porous substrate and enough flow will do the same thing as a small filter. In a standard aquarium. 50% of the bacteria are in your filter and 50% are in the substrate and maybe a few percent in the water and on the surface of plants and glass. 

You'll need flow anyway, whether this is a filter or streaming pump so a filter is just an extra buffer for when you disturb the substrate (which will be your biological filter without a filter). Also, the bacteria in a filter will work better than the ones in the substrate because they receive more 'food' because the flow is better than in the substrate. It is also established faster than the bacteria in the substrate but if you have time and won't uproot or disturb the substrate too much, you can get away with just a streamer.

The filterless reeftanks are not so filterless, they use a lot of live rock which act as filter..

IMO, pro's filter over just substrate:
- you always have the substrate so you double the biological capacity
- established faster because more flow
- when you disturb one (substrate/filter) you always have the other to buffer
- easy to add other chemical media (carbon or peat or anything) without hanging it in the aquarium
- mechanical filtration, the filter will also collect dirt particles, which otherwise end up in the substrate or keep flowing around, making the water less clear.
- connect other instruments like heater, external CO2 reactor, UV unit

(and no I don't have stocks)

Do you really need a filter, NO, only vacuum a part of the substrate a time, don't uproot too much and use a porous substrate and provide flow over it and without too many fish you'll be fine as well!


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## AquaBarren (Nov 6, 2009)

Yo-Han is right on. You will need water movement though. 

One thing though. Every filter has a practical limit. Your bio load in the tank may require more capacity than the "tank" can provide on its own. A filter provides the extra capacity. So "fully stocked" is relative. 

Also, don't undervalue mechanical filtration. It has a role too.


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## Dr_Hoatzin (Aug 29, 2011)

AquaBarren said:


> Also, don't undervalue mechanical filtration. It has a role too.


Agreed.

I think you could run a tank with a false bottom, have the water trickling through a porous substrate (thick layer of crushed volcano rock or porous ceramic media underneath standard substrate?) and down to a reservoir/return area would essentially filter the tank. But...that means you're keeping all your filter media in the tank. Which means less room for everything else. And most likely a lower stocking level, to boot.

But i'd love to see pics of how it works, if you build it.


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## niko (Jan 28, 2004)

Yes you can run your tank without a filter. When you remove the filter you will see that the plants actually grow a little faster and look a little better. That's because without a filter more nutrients are available to them.

It is all good until your tank crashes gloriously. 

The filter is an insurance. It is NOT NEEDED when things are running just fine. But even if you maintain your tank exactly the same way every single week one sunny day something will change. The tank is not an isolated world with you as its god. It reacts to the seasons, to interaction of substances that accumulate gradually in it, to magnetic fields and other things. 

One good thing to note is that many people run their planted tanks with ridiculous filtration and still manage to keep them clean. Maybe one day in the future everybody will nail it in their head that filtration is important and there will be less issues. If you look at both planted tank forums now you can see posts about issues all over. That is partly from not knowing the basics of running an aquarium, but HUGE part of it is not knowing anything about how the filter works. Yo-han here has an excellent post about what is the biofilter. That is the only such post on an American forum. That says a lot.


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## chagovatoloco (Nov 17, 2007)

Actually, I have had one tank running with out a filter for a few years. I also have a fifty gallon that is running with out a filter but only for a few weeks. I do have a hob filter but it has no media, and a powehead as well. I have seen the importance of water movement first hand. I was have also done the whole hight tech thing, successfully. I do little to no maintenance on my tanks now. And Spend more time letting what will happen happen. I have no problem keeping fish or plants happy. Yes some stuff floats around and I have green spot algae. But I'm happy and plants grow. I don't now what being an American has to do with it? Nor do I think I'm god. I will ignore the fact that your trying to offend me and humbly ask why do you think it will crash? 

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## rjordan393 (Nov 23, 2012)

For a planted aquarium; Yes, but only for the nitrogen cycle. If you got the time, read these 18 articles authored by Carl Strohmeyer on the reasons for maintenance of aquariums.
http://www.americanaquariumproducts.com/AquariumKH.html


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## BruceF (Aug 5, 2011)

I find that in tanks without filters the main thing is that you have to restrict the number of members of the animal kingdom you allow. I have a ten gallon tank that has been running for 2 years with no filter, no heater and nothing to move the water at all. It is essentially a tank full of dwarf sag that I grew until it filled the tank. The only residents were snails for the most part. Last fall I kept 6 baby Odessa Barbs in it for three months. I just did 50% water changes once a week. 
By all other standards I under filter all of my tanks but I never keep many fish in them. For the most part I use internal filters and often these are nothing more than a power head and a sponge. I wouldn’t say that I have no problems but I would say I don’t have any more problems than the people who run sumps with all the high tech bells and whistles.


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## houseofcards (Feb 16, 2005)

Yo-han said:


> This is true! A fully grown tank with a porous substrate and enough flow will do the same thing as a small filter. *In a standard aquarium. 50% of the bacteria are in your filter and 50% are in the substrate and maybe a few percent in the water and on the surface of plants and glass. *


I'm not sure what you mean by a standard aquarium, but most aquariums on the forum anyway are 2 to 4 ft rectangles with a canister filter. I would say once the tank is established especially with plants in it 90% of the bio-filter is in the tank not in the filter IMO. The filter for the most part is a flow device depending on what media you have in there. The exception to this would be a small tank with some ridiculously large canister filter on it. The gentle flow through most tanks is more than enough to deliver ferts/co2 and to have the bacteria do there job.


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## Diana K (Dec 20, 2007)

The standard aquarium in the quote is probably any size tank, with HOB or Canister filter with a water movement of between 3-10 x the tank volume per hour. The filter probably has a volume of perhaps 1% to 5% of the tank. The filter is filled with sponge, foam, perhaps chemical media (activated carbon, other) and bio-media. 

Example: 
20 gallon tank with a Penguin 170 (discontinued, but it is the one I have on my 20 long) HOB. 170 gph. Volume is 1 quart (I just measured it)
1 quart out of 80 quarts (20 gallons) is 1.25%. 
170 gph is 8.5x tank volume per hour
I have added more media to this filter. It was originally a cartridge style. I have packed it with media like an Aquaclear, lots of coarse floss, bio noodles, and added a sponge over the intake. 
So my example is probably a lot more filter than is standard on an average tank. 

Example: 
29 gallon (standard) tank with Fluval 204 canister. 
volume of the canister is 4.6 liters, or 1.2 gallons
flow rate 680 lph = 180 gph
so... 
volume of filter is pretty close to 4% of the tank,
Flow rate is 6.2x the tank volume per hour.
Standard filter media: Sponge, medium and finer floss, peat moss, bio noodles. 

Anyway, in either of these samples I would assume that roughly half the nitrifying bacteria is in the filter media. They actually have something close to the same flow rate (170 and 180 gph) so high oxygen, good supply of ammonia and other nutrients in the filters. 
The other half of the bacteria is all over the tank, on all the surfaces that suit these bacteria. 
~ Out of the light, so not on the upper surface of the substrate. 
~ Good water flow (high oxygen), so not deep in the substrate. 
the bacteria will live best on the top fraction of an inch of the substrate. Perhaps 1/4" to 1/2" deep on a gravel substrate, but not more than 1/4" deep on finer substrate (sand). However, aquatic plants add oxygen to the deeper layers of the substrate, so there will probably be more bacteria in our planted substrates than in a gravel in a tank with no plants. Still, there is not so much surface area that the population will be higher than in the filter. 
~Other places with LOTS of surface area, so there will not be much on smooth surfaces like glass walls, heater or ceramic merpeople. But lots of surface area on porous rocks (lava) and driftwood. 
On the surfaces of the plants where the conditions suit the bacteria: Good water flow, not in the direct light, so under the leaves, on the shaded stems, and on the roots, since the roots add oxygen to the substrate. 

I also have not done actual experiments. The closest I can come is some very rough numbers. I have used several established tanks to set up a new tank. Getting the new tank up and running very quickly, and lightly stocked right away. It has been several years since I did this, and I did it a lot, mixing many sizes of tanks as donors and new tanks, so I cannot be more precise than to post my general rules for how I did this. 

I have removed as much as 25% of the filter media from a well cycled tank (long running, fish only or fish and plants) and used it to set up a new tank. 
By sharing the media from several tanks I was able to fully stock the new tank, and by taking not more than 25% of the filter media the donor tanks did not suffer an ammonia spike. 
My assumption is that 25% of the filter media represents about 1/8 of all the bacteria in the system (tank and filter combined), and so could support about 1/8 the bioload of the donor tank. 
The new set ups were stocked lightly, perhaps 1" of fish per 2-3 gallons of water for a week or so, then increased before the bacteria could die off. 
The donor tanks were stocked at something closer to 1" per gallon. Sometimes a few fish were removed from the donor tanks to partially stock the new set up. 

When plants are in the tank, then they sure are part of the bio filter, so in that sense you can sure argue that way more than 50% of the bio filter is in the tank. I would think that the bacteria distribution would not be far off the 50/50 distribution, though. There just is not that much surface area in an aquarium (with or without plants) compared to sponges, floss and bio-noodles found in the average filter. 
The total nitrifying bacteria population will be a lot less in the planted tank, since the plants take a lot of the ammonia before the bacteria can get it. The most obvious way to prove this is to remove the plants and watch the ammonia spike! (Poor fish! Please do not do this.)


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## houseofcards (Feb 16, 2005)

Diana K said:


> ...Anyway, in either of these samples I would assume that roughly half the nitrifying bacteria is in the filter media.


I'm not sure how your getting that.

In mature tanks with or without heavy plant load, I have shut off my filters either on purpose or by accident for days on countless occasions and never had an issue. The only thing I notice was the plants would pearl heavier since the bacteria in the filter was dead and not consuming O2.


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