What's the point of a filter?

[CoyoteWildfire]

This probably seems like a no-brainer of a question, but why use a filter?

If the mechanical filtration can be done via a gravel vaccuum, the water is stirred via good aeration, the bacteria grow in the gravel and on other surfaces, and you don't have any sick fish that you would need the carbon for...why bother?

 

[Shadowraven]

A filter can serve several purposes that tank maintenance can't.

First of all there is mechanical filtration. Mechanical filtration will remove the particulates you have floating in the water. This can be food, fish feces or the detritus you stirring up while vacuuming the gravel. It can also remove some of the proteins that cause film on the surface of your water.

Next is the biological filtration the filter provides. It provides a stable home for your good bacteria to colonize. Without this, anytime you vacuumed the tank and disturbed the substrate you may be removing and killing off the bacteria you need to keep the water quality stable.

Third there is chemical filtration. Chemical filtration can remove odors, ammonia and other potentially toxic gases and elements from your water.

Finally there is the aeration aspect. Water moving through the filter is being oxygenated as it flows through it. The outflow into the tank also improves the water's oxygen uptake. Its disruption of the surface tension can also keep any protein waste from coating the surface of the water.

 

[Crepe]

A filter can serve several purposes that tank maintenance can't.

First of all there is mechanical filtration. Mechanical filtration will remove the particulates you have floating in the water. This can be food, fish feces or the detritus you stirring up while vacuuming the gravel. It can also remove some of the proteins that cause film on the surface of your water.

Next is the biological filtration the filter provides. It provides a stable home for your good bacteria to colonize. Without this, anytime you vacuumed the tank and disturbed the substrate you may be removing and killing off the bacteria you need to keep the water quality stable.

Third there is chemical filtration. Chemical filtration can remove odors, ammonia and other potentially toxic gases and elements from your water.

Finally there is the aeration aspect. Water moving through the filter is being oxygenated as it flows through it. The outflow into the tank also improves the water's oxygen uptake. Its disruption of the surface tension can also keep any protein waste from coating the surface of the water.

I'll have to disagree with many of your points:

1.) Mechanical filtration isn't totally necessary in a tank at all. Most salt water tanks forgo mechanical filtration because trapping a lot of organic particles in one spot makes a nitrate factory. Additionally, what organic particulates you do catch in your filter floss or what have you eventually will break down anyways and its chemical products should be dealt with by the biological portion of the filter.
2.) Chemical filtration is completely superfluous in most cases. Sure carbon can be used to remove medications but that's a very rare circumstance. Most tanks do not need any form of chemical filtration at all. I haven't used carbon in any of my filters in about 5 years.
3.)Aeration isn't the function of a filter. Rarely have I seen anyone use a spray bar to move water at the surface. HOBs inherently cause surface agitation but the movement of gasses should be easily facilitated by the stagnant surface area of the water. It helps but isn't 100% necessary. A canister filter doesn't aerate the water like a HOB would...
More importantly is flow which I'll discuss next.

Biological filtration in my opinion is the single reason we have filters. The reason we have filters and don't just rely on the substrate for filtration is because there is little to no water movement in the substrate. Thus ammonia rich water won't be in contact with the bacteria and thus won't be reduced (technically oxidized) into a more friendly state. A filter may not substantially increase total surface area with in a tank but it will increase bio-available surface area which is a combination of the density of bacterial growth and its effectiveness. Flow is a very strong factor in the balance of a tank. It keeps small particulate waste suspended in the water and forces water into and through the substrate and through the biomedia. You can't have a biologically balanced tank without flow. Often times freshwater aquarists fail to realize flow is as important in fw as in sw. You just need less of it.

So to sum things up:
No, you don't need a filter. A few power heads will do fine. However, you will not be able to stock your tank to maximum capacity. Maybe 1/3 of the fish you would be able to with a filter.

Even then you don't need power heads but again, expect to reduce your stocking levels significantly.

on a side note...yes protein films are disgusting but what can you do lol.

edit: nevermind I've used carbon just last month to clear up my tank after digging around the substrate.

 

[Shadowraven]

I see that I am still not explaining myself well enough. Sorry it's a flaw I'm trying to fix. In answer to your response crepe:

1) I didn't mean to imply that mechanical filtration was absolutely necessary, just that many filters perform it. However, it still is occasionally useful for clearing the water. I still use it for just that.

2) You're right again that chemical filtration isn't always necessary. I didn't mean to say that it was. But it has its uses as well. I prefer to use it myself. It is great for removing those fishy odors.

3) Aeration IS NOT a primary function of a filter. It is a secondary benefit. I never meant to imply that is was. I said what it did, not that it was designed to do so. However, whenever you disturb the surface tension of a body of water, you ARE aerating it. The filters I design are made to aerate the water in the filter and I often attach the water return to a spray bar.

4) The filter keeps water moving through the tank so that there are fewer dead spots. That allows the entire water column to be processed through the biological filtration portion of the filter.

5) Finally, the only truly necessary part of the filter is the biological component. You already did a very good job of explaining that yourself, so I won't go into it here.

In short you can see that we mostly agree on what a filter is for.

Where we depart is when you state that they are not necessary. I couldn't disagree with you more. The filter provides a stable platform for your bacteria and mixes the water column in the tank through the media so it can do its job. My tanks have always done better when they had a filter running as opposed to not having one.

 

[CoyoteWildfire]

Fascinating. I was leaning toward a lot of what you said Shadow. I will still continue using my dual filtration on my 29G, but I was curious about the reasons behind continuing to do so.

I knew that there was a good reason--a stable biological filter, primarily, that wouldn't be disturbed by gravel vacuuming--but I wanted to know what exactly those reasons were and what the opinions were.

But knowing I could also get by without a filter (by stocking a lot lower) is an interesting thought. I wouldn't mind experimenting with water and plants (no fish), and cycle my tank that way and see how it affects the cycle, it's speed, the quality of the water and its clarity and other such factors. Interesting food for thought, in my opinion.

 

[Shadowraven]

It is possible, but there are other reasons I avoid it. Most of the fish that we aquarists keep aren't from extremely still waters.

Most of your South American (tetras and corydoras) and African species (african barbs) come from streams and pools of water with a distinct current. A still body of water is not the environment they are adapted to. Yes, I know that aquariums aren't natural enviornments either. But we usually try to replicate them as much as posible, don't we?

Many Asian & Australian fish (barbs and danios) come from lakes, rivers & streams as well. There are several Asian fish that also inhabit still pools in rice paddies and along roadsides. Bettas are one fish that comes to mind here. Most anabantids have the adaptation necessary to inhabit these low oxygen enviroments. That is why they have the labyrinth organ to breath atmospheric oxygen. You can read further if you want to know what other fish do as well.

Although there are some North American species that enjoy still waters, most of them also come from lakes and streams.

 

[CoyoteWildfire]

Yes, certainly. I would be doing my research as to what kinds of fish prefer still waters rather than flowing before attempting a filterless environment. The Dwarf Gourami also has the labyrinth organ, and tends to startle easy, which is why they too tend to thrive in stiller waters.

I must agree, we do want to replicate their natural environments as much as possible. I can't stand to see puppies or kittens in pet stores that are just existing in this tiny 3x3x3 cake, sitting away in their own feces with nothing to do.

Obviously, I wouldn't want that to be the case with my fish, either.

 

[Shadowraven]

Sounds like you've got it under control. If you decide to do it let me know how it goes.

 

[CoyoteWildfire]

Will do. Thanks Shadow!