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An (excited) word about filtration

97K views 313 replies 52 participants last post by  BriDroid 
#1 · (Edited)
I got excited or something discussing cheap and powerful canister filters made in China. So I jolted down some words of wisdom. Could be an eye opener for someone.

A few details have been ommited. Like what kind of glue is best to keep your fish in one place after you hook up a crazy powerful pump to your filter and have 0 algae issues.

Here it is:

It really annoys me to see filters labeled "for XXX gal. size tank". That's the dumbest claim ever.

Virtually all canister filters on the market are equipped with motors that are completely inadequate. Or rather - the motors belong to filters that are at least 1/2 the size of the housing.

Here's how it works:
There is a publication, a scientific one, about the water turnover through a filter that will provide 100% filtration. Running 1 tank volume an hour through the filter does not mean you have filtered all the water in the tank once. That's because the water being sucked by the filter is a mix of filtered and unfiltered water.

So, to make this simple - the water in an aquarium needs to pass through the filter 9.2 times in order to be filtered 100%.

Ok, so for my 100 gal. tank I need a filter that pumps 900 gph? No. I actually need more. I need about 40% more flow because of the resistance of the filter media, hoses etc. So to filter 100% of the water in a 100 gal. tank once every hour I need a filter pump that runs 1200 gph.

Wow!

And there is something else. There is an optimal volume of the filter media in relation to the tank volume. It is 8-10% of the tank volume. So for my 100 gal. tank I need a filter that holds 10 gals. of media.

Another "wow"!

And of course there is more. The filter media area is important. Meaning that I cannot get the smallest cheapest canister filter, hook up a 1200 gph pump to it and cover all bases. Simply put the volume of the filter and the pump output need to match. For my 100 gal. tank I need a filter that holds 10 gals of media and 1200 gph pump. But these 10 gals of media better not be stacked high. They better be spread as wide as possible. The thickness should not be more than 6.5 inches.

Wow...

No, that's not the end. There is a scary part to it all too. The same bacteria that happily eats your fishes' waste and makes Nitrate from stinky and toxic Ammonia will actually do the opposite if the flow through the filter media is too slow. So on Monday my bacteria eats Ammonia and produces Nitrate. On Tuesday my filter is slightly clogged and some of the bacteria now makes Ammonia from the Nitrate that their buddies produce. On Wednesday... you get it - most of the bacteria could be making Ammonia.

More... The bacteria in the biofilter is not just bacteria. It's all sorts of animals that gradually evolve and establish themselves. Think of it as the History of the World. Civilizations rose and fell. It's never the same. Now imagine what would happen if someone swept the place clean every 100 years or so. Started anew. There will be no real history. No humans. No internet!!! My point is - when you diligently rinse your filter every week or every month you are doing exactly that - resetting the development of your biofilter. Harming it. What is right to do is to choose the proper media that does not clog easily and does not need frequent rinsing.

Yes there is more... but enough said.

All of that makes my head hurt. Because when I see filters labeled "for up to 290 gal. tank" it's as if we all understand the conditions. And we don't. I bet this is the first post that explains filtration somewhat clearly to you. I've been in this hobby since 1981 and only the last year heard about all these things.

Basically if the filtration is properly setup you do not need mechanical filtration. You will seldom fight algae. There will be wars and fails and victories that you will never see - your bacteria and Co. will take care of it all for you.

Or one can just enjoy this hobby. It is not said we all must do things "the right way". It's about having fun, right.

--Nikolay
 
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#287 ·
They don't pull out the Nitrites/Nitrates but what they do is clear out the partials of the water. They do require a balance of bioload and plants to help keep the nitrates low. One of my tanks(one shown) bioload was to heavy for them to survive. I found them all dead this week in that particular tank. When one dies, it can quickly foul up the water and cause nitrite/nitrate spike which will kill the rest in your tank. This tank had a HOB filter on it. The other tanks all have canister filters on them which keeps the tanks clean and water moving.
 
#296 ·
I can't help but imagine one of those shallow, broad reef tanks (36"x36"x8") as the filter box sitting adjacent to and slightly above the aqaurium, with one side trimmed down in such as way as to flow into the aquarium. That'd be one heck of an expensive filter box, but it'd sure hold a lot of media and allow for some good flow.

Anyway, this thread is a tremendous help in tackling the "why" and "what" of filtration. Thanks for letting me spy in on it :spy:
 
#303 ·
Cheap plastic is an understatement. Have you seen plastic disintegrate like bread soaked in water? That is what happened to one of my cheap Chinese filters. I can't even explain how the plastic looked and felt to the touch.

No commercially available filter is designed well except maybe ADA's. The first thing that is a problem is the insufficient canister/box volume. The amazing idea to stuff both mechanical and biological filtration in one housing is the next bad thing. Then there are the insufficient flow rates, the stupid hose connections, ugly in and outflows, hard and/or ugly hoses made by the Adams family and so on.
 
#309 ·
Actually the Japanese have not figured out a filter that stays clean for a long time. At the time I posted that I didn't know. ADA's pumice serves as both biomedia and mechanical media. Meaning that it does need frequent rinsing (about once a month).

ADA's filter media and its maintenance is a trade off - you get a cool looking canister filter that it is easy to fit under the tank. You do not mess with different medias. That's all fine and dandy but it relies on the tank running very clean. That's why their tanks have few fish. Try overloading the tank with a few extra fish and all that "amazing" filtration system will peter out in no time. As always - a part of a system works only within the frame of the system. But in this hobby most people don't think even close to that. It's all about cheap, easy, more is better and so on.

Luminescent,

Your filter sounds too complicated for the average hobbyist. No matter how well it works. The average planted tank enthusiast doesn't even know the basics of filtration.

One thing in your description is interesting to me - the spinning spray bar. I've been looking at some UK designed filters that self clean by using a spinning spray bar. In your case I assume you installed that spinning spraybar to ensure even flow of the water through the lava rock in the 5 gal. bucket. Are there any other reasons to use that spinning spraybar?

Also, look here. I heard that yesterday on radio. It's indeed amazing how way off most of us are in understanding or willing to understand this hobby:
http://www.aquaticplantcentral.com/forumapc/filtration/88696-you-need-read.html#post660029
 
#310 ·
Luminescent,

Your filter sounds too complicated for the average hobbyist. No matter how well it works. The average planted tank enthusiast doesn't even know the basics of filtration.

One thing in your description is interesting to me - the spinning spray bar. I've been looking at some UK designed filters that self clean by using a spinning spray bar. In your case I assume you installed that spinning spraybar to ensure even flow of the water through the lava rock in the 5 gal. bucket. Are there any other reasons to use that spinning spraybar?

Also, look here. I heard that yesterday on radio. It's indeed amazing how way off most of us are in understanding or willing to understand this hobby:
http://www.aquaticplantcentral.com/forumapc/filtration/88696-you-need-read.html#post660029
-------------------
I would never make anything that intense for a planted tank. That was for a reef system. But there is no reason not to use things like lava rock (lightly rinsed my buckets out about every 6 mos with Oceanic water) and large pore pre-filter sponge (in the corner overflow compartment on the back corner of the tank- it was bottom drilled).

The coarse pre-filter sponge was rinsed in my partial water change water once a week.

We used to make the spinning spray bars when I was a manager at a large aquarium in the 80's.

Another reason for them was to boost oxygenation of the water after the prefilter and before it hit the nitrobacteria in the lava rock.

How you drill the bar- the force of the water makes it spin, like in your dishwasher. I just found a pic of a guy holding a giant one for a pond.

The important thing is the pre-filter, it's necessary to prevent hole clogs.

I made my spray-bar to fit just inside the top of a 5 gallon bucket and cover the media thoroughly as it spun.
 
#311 ·
Hello All

I have been a vivid reader of loads of posts here, though havent posted myself. I am from Swissland, in Europe. Have a 45 gal tank (had another 70 ltr, but gave away for lack of time), well planted, with CO2. Will detail my tank in another post someday soon.

I have been reading this post with interest, and have a few observations to make; hence this post. Please forgive me for intruding, and apologies if I manage to not convey properly (english is not a Swiss language..). Feel free to criticise my personal opinions (in a civilised sense)..

The intentions of the OP (original poster) are well and meant for not so naive enthusiast, but are very qualitative, empirical, and draw loads of heuristic inferences without actually understanding the details of scientific facts and rationale. Plus there is a lot of bashing going around for methods and concepts which people either dont like personally, have issues with their originator, or simply dont understand (EI & Tom Barr is a prime case here). I also observe a huge amount of blind following: since ADA has done this (looking only at their pictures & advertising catalogues; not necessarily grasping the science behind), this MUST be the only way... kind of faith-based reasoning..

But as someone pointed out, different methods work for different people. I gather that the discussion is mainly a scientific one.. Many posts are indeed in this direction, but most are not.

Aquaria are semi-closed systems. We intervene the tanks so as to mimic natural processes: flows, filterations, CO2, lighting, fertilization etc.. I am specifically talking about planted tanks (any taste: el natural, hi-tech, ada style, dutch/nature scapes..). Basic principle would be to provide all the things that plants need to grow, sustain and flourish.

Lets take ferts: ADA & Walstad types follow this through substrate. ADA is a processed clay that has high CEC, is breathable, and has loads of slow-release ferts (macros mostly) that get leached out to the water with time. These guys have done research on different water types (kH, pH, gH, etc), and timescales needed for these ferts to leach out. Thats why they have a different liquid fert dosing schedules depending on how old/new the tank is. This way they have made sure that plants can access required amounts of ferts (via roots) & also via water over the lifetime of Amazonia. Then they suggest you to replace it. But most hobbists neednt. Adding osmocote or similar balls deep into soil periodically mimics the ADA type substrate dosing, supplemented by water dosing. Other methods like EI, PMDD, etc have differing routes to provide ferts to plants. There are loads of great tanks out there which use inert but high CEC substrates like Akadama, or even small bonsai soils (essentially heat tempered clay) with very high NO3, PO4, K levels in their waters and never have algae issues. In a scientific discussion these methods shouldnt be boycotted. There are scientific methods & ideas behind them. If things are too complicated for you, doesnt mean that those methods are dead wrong..

The main topic in the current posts is filteration:

We all use impeller pumps in our cannisters. They are limited by pressure heads since they push water from the cannister through the tube towards the tank. Longer/higher the tank & cannister-o/p tube length, less the gph flow rate.. And rather than simply getting excited about these rules "10X the flow" & "cannister volume should be at least 10% of tank volume", because Ada or someone else has done this & their pictures show this, stop and ask why? There are loads of posts on the size of lava rock, should it be broken, or should I buy Ada rocks, is rock better than something else...., again ask why? Below is one simple calculation one might do so as to try justifying the numbers we get to see around, etc.. This is just 1 example. My point is we ought to always demand a reasoning.. not behave like cult fanatics.

Assume the tank has a volume V gallons. If I assume (simplistically, ignoring the difficulties etc) that my cannister provides a 10X flow through the tank, then the flow rate is 10V gph. Now assume that my cannister is 10% volume of the tank. i.e. cannister volume is V/10 gallons. This means my cannister water is being replaced 100 times per hour ( 10V gph / [V/10 gallons] = 100 / hour). This is 100 * (V/10) = 10*V gallons of water gets flushed into our cannister per hour. Now starts the tricky part. Given the volume of the media inside the cannister, one needs to know how much of this water is being seen by the bacteria/microfauna sitting in those lava rocks or whatever.
The water is sitting in a volume, but the bacteria live on the surface. So how much water do these bacteria actually process? This comes in three parts: the contact area of the water with bacteria, how fast the water flows past them, and how long do the bacteria need to process a given amount of water in their contact.

The first will depend on how "porous" the material is & how fast it gets clogged. From school geomerty we know that for a sphere, the volume is (4/3) Pi r^3, and the surface area is 4 Pi r^2. So assume that all lava-rock spaces are small spheres. Then the fraction of water inside each sphere that "touches" the surface of the sphere (& hence the bacteria) is (Area/Volume) = (3/r). So smaller the size of these spaces (i.e. small r-value), more is the amount of water available to bacteria to feed on). But if the stuff starts clogging, its useless. Hence we ought to do mechanical filteration beforehand, and periodically clean the filters. (The clogged muck also increases the BOD, etc but thats another dimension to the story).

We already know the answer to the second issue: how fast water flows past the media. The third one i.e. how long it takes for bacteria to process the water is complicated, and depends on which strains we are talking (there are competing strains here, some which increase NO2, some which increase NO3, each with differing lifetimes, efficiencies; how much aerobic/anaerobic the place is, etc..). Perhaps a trained person (Phil??) can shed light into this. Would these timescales of bacterial water clensing, water flow-rates and availability etc match the tank & cannister specifications, how one can improve the biological filteration?? BTW, this will also depend on the biomass in our tanks.. yet another variable.

So then you start to see how to figure out the reasons behind the successful tanks/methods. The tank itself provides a HUGE biofilter in itself. All the stuff inside the tank including the substrate has a biofilm full of microfauna doing exactly the same job as your filter bacteria.

I really didnt understand why there was so many posts on the flow pattern needs inside the tank. The flow in the tank is needed for maintaining a uniformity in, say, temperature, fert & CO2 availability, and transporting locally generated organic excretants ultimately to the filter to get cleaned. For such a need, clearly a lamilar flow that is self-constructive (i.e. follows a U- or sircular pattern accross the tank), and reaches every nook and corner of the tank is desirable. The flow speed should assist the transport of ferts to plant leaves. As I mentioned above, plants have an active biofilm around them. Plus water has high surface tension, which means there is a boundary layer between the tank-water, and each leaf/plant. This layer prevents/stops easy transport of ferts/CO2/O2 accross the plant & surrounding water. Thats why stagnant water leads to mushy plants.. The flow speed should be such that it helps fert transport accross this layer, but not too fast so as to damage the leaf cell structure. An easy ball-park estimate of this is "all plants should essentially sway in the flow".

Turbulent flows lead to eddies/vortices that hinder any of the above & hence should be avoided. The water simply keeps moving round&round in ever decreasing circles withough actually going anywhere.

Clearly lily-pipes and/or spray bars, and/or well designed HOB type filters, and/or Koralia type pumps all, when placed properly, achieve this. Aesthetic choice is yours, but please dont try justifying Ada lily-pipes alone because nothing else worked for you, and that Ada has done this, so it must be the ONLY correct way. Understand the basic geometric requirements, flow patterns in your hardscaped tanks, and then proceed.

Ok, I will end first part of my ramblings. More to come, but feel free to comment. Just remember that in Europe, or far east large number of hobbists have great tanks, fantastic scapes, very active flora & fauna in their tanks (even non-Ada ones!!). We all play around, but surely apply some scientific means (if you are that inclined; you can succeed using only common sense & without the need for all the deeper understandings).

cheers
niru
 
#313 ·
Very well said Niru. I wish my German, French, and/or Italian were as good as your English!

I'm sorry, but microbiology is one of my weaknesses. I don't know off the top of my head how quickly different strains/species will process the C, N, and P in a system. I'm of the opinion that each system is unique so making generalizations about microbial uptake is pretty much useless to. My belief/philosophy is to move water as slowly through the filter as possible while maintaining a wholly aerobic environment. The more contact time water has with media and microbes the better it's going to get cleaned. Filters are there mostly to process biological wastes and organic molecules into inorganic ones that the plants can then take up easily, in my opinion. As such they're a supplemental, but essential, part of the whole system's filtration capacity.
 
#314 ·
Well said Niru. I feel similar to you, there is no right or wrong way to have a beautiful planted tank. I get sick of reading someone post "it's all your fault cause you didn't do X", instead of helping them grow and learn different techniques.

Thank you for posting that!
 
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