Tropical Fish Keeping - Aquarium fish care and resources

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JDM 12-12-2012 08:04 PM

To filter or not to filter....
Well, not really. I know that one member here flogs the idea of filterless tanks, (you know who you are), and I actually started out at the LFS with that question on my mind... Some sort of self sustaining biosphere in a tank. Then I realized some of the factors that are at play in a tank...workable but not really what I wanted to end up with... expectation vs reality.

I wondered about under filtering, using a 20 instead of a 30 on a 25 gal tank. Then I see Byron's comment on another post as follows:

"but you are going with live plants and that makes a big difference. Remember that a well planted tank that is not overcrowded and has the right fish for compatibility does not really need a filter at all. So when we add one, it doesn't have to be monstrous, as it will just be detrimental to fish and plants."

"...doesn't have to be monstrous...", what does that mean exactly?


Canadian Fish 12-12-2012 08:12 PM


Originally Posted by JDM (Post 1346958)
"...doesn't have to be monstrous...", what does that mean exactly?

I think (he'll clarify) that he mean the filter doesn't have to be ridiculously over rated for the tank. Ie it's probably not a great idea to have an Aquaclear 70 on a 10 gallon tank. This is obviously hyperbole, but I think that's what he was getting at.

Mikaila31 12-12-2012 09:48 PM

In a well planted tank with good growth all you are really looking for is sufficient current. I do have one filterless tank currently and another that would be fine without a filter but uses one anyway.

Geomancer 12-13-2012 06:04 AM

Think about what a filter does. A regular filter with sponges, pads, & bio media.

Does it remove Ammonia & Nitrite? Not directly, the bacteria living in the filter does, but it lives everywhere in the tank and far more of it is in the substrate of an established tank. People with carteridge HOBs throw the catridge out once a month and don't loose their cycle.

Does it remove Nitrate? Nope.

Does it remove organics? Nope.

Does it remove well ... anything? Sort of. It traps solid wastes that are suspended in the water. Fish poop, uneaten food, plant mater, etc. It still bio-degrades in the filter though until you clean it out.

Cleaning out a filter is generally easier than cleaning out the substrate, plus it makes the water look more clear which most people want because it looks 'clean' (but actually isn't very natural). Another use (and I would say the actual primary reason) for filters is water movement, some is needed to keep an even temperature throughout the tank and to move nutrients around for the plants to get access to them (if you have plants). Smaller tanks can do fine with just convection but I'd be hesitant to try it with larger tanks.

A lot of fish don't like strong currents. They come from swamps, flooded stream banks, or very slow moving rivers. They act far more natural if they don't have to fight a current 24/7 to keep from being blown around. Now, some fish are an exception to this that do actually come from fast moving rivers, but most like calm water.

As an aside, I'm aware some people use organic absorbant materials in their filters, like Purigen or similar, but the majority do not. Activated Carbon may remove some stuff, but it gets used up so fast, and replaced so infrequently, that for most people it isn't doing a whole heck of a lot most the time.

I'm using a basic sponge filter on my 10 and 20 gallon tanks, and on my 125 gallon tank I use a canister fitler that's rated exactly for 125 gallons on the box (I never even looked at the gallon/hour numbers). Water quality is perfect, thanks to weekly water changes and lots of live plants, the best true filters you can have.

JDM 12-13-2012 07:18 AM


Since doing my little research on ammonia etc, I figured out that the filter doesn't do much other than what you mention. I already knew that I needn't be concerned about the carbon part of the filter, not worth having to buy a new one every month or so. I am now considering whether I need the bio-media part as well. I suppose it can't hurt and is only 1/3 of the filter media in an Aquaclear anyway.

Like you said, circulation is the main factor as well as filtering out suspended solids. In the interest of cleaning up the tank area I might be better to go with a canister filter with sponges. The only issue then is the sponges are out of sight and therefore out of mind so I would need to pay attention to the flow to know when to clean them... at least until I get onto a schedule.

I was looking forward to the little trickling sound of the HOB filter, we used to have a rather large water feature in the family room which is now outside for space considerations.


AbbeysDad 12-13-2012 09:30 AM

There is a prevailing myth that the filter rating needs to be 4 to 10x the tank size in gallons per hour (GPH). Even some die hard members here, with very messy fish are proponents of this. I call it a myth because good filtration/purification is not about how much water we push through a filter, but how well the filter traps very small particulate matter. Trapping the organics is just phase one as it's here that facultative bacteria break down the organics in a process of rot and decay. To some degree, this results in dissolved organics that somewhat muddies the water.

In a well planted tank, especially one that receives a 50% weekly water change, with the exception of necessary circulation, the filter is almost optional. Mulm that settles on the bottom slowly decays and organically feeds the plants (just like organic gardening and mulch). Even without plants, mulm creates a healthy function in the aquarium. However, many fish keepers don't like how it looks. Some will even go so far as to use power heads for even more circulation so the filter 'removes' the mulm. But the filter just quickly converts this to polluting dissolved organic solids.

I used to buy into the bio-media hype, but I've come to a place where I believe that open cell foam sponges are every bit as good a platform for beneficial bacteria. I am currently using Purigen to adsorb dissolved organics and may occasionally use activated carbon. I still fight the good fight of high nitrates in my well water.

Frankly the filters we have today continue to fall short in purifying water, which is why we must do weekly water changes. After all, commercial aquariums with millions of gallons don't do 50% weekly water changes...they don't have to because they have very sophisticated filtration systems.

Sooo... In general, for my nichol, I believe we should choose a filter rated for the size of the tank as oversizing the filter just creates excess current that stress many fish species. After all, if you can't achieve clear water by filtering every drop 2-4 times an hour, blasting more water through there isn't going to help! :-D

fish monger 12-13-2012 09:55 AM

I like the idea of having minimal filtration just for the sake of slight water movement. Even stagnant ponds receive some surface agitation from breezes. Filters, in my opinion, are a safety net that we provide for our enclosed systems.

1077 12-13-2012 12:15 PM

I am completely satisfied with the filtration on all of my tanks, and do not believe in the myth that slower flow,choked back flow, which allows more suspended solids to fall to the substrate,is the way forward.:lol:
I have yet to see anywhere other than here ,this myth about slower flow being better, substantiated.

fish monger 12-13-2012 01:44 PM


Originally Posted by 1077 (Post 1347453)
I am completely satisfied with the filtration on all of my tanks, and do not believe in the myth that slower flow,choked back flow, which allows more suspended solids to fall to the substrate,is the way forward.:lol:
I have yet to see anywhere other than here ,this myth about slower flow being better, substantiated.

Well, I know what you mean. To each their own. I do think it's a matter of interpretation. Bet our degrees of filtration are closer than farther apart.

twocents 12-13-2012 04:31 PM

am I flogging? never said I don't have filters... just not canisters..
do we really need filters??

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