Chicken & Egg

[Big G]

This is going to be such a rudimentary question that it will just be assumed knowledge for most….but not for me so ;

I’m delving into filtration and gorging on it on UKAPS and Aquarium Science (not least of which is that sponge, k1 and pot scrubbers are arguably , cubed inch for cubed inch, the best ‘forward operating base ‘for biological denitrifying bacteria of all possible viable filter medias).

Anyway, I’ll dig further on this before removing all my expensive pumice, which if this is true makes me frankly, a bit of a marketing-led idiot and turn instead to impeller pumps. I’m going slow for my sake not yours , so if I comes across as either patronising or ‘splainy, that’s certainly not my intention nor desire. Far from it, I have both the utmost respect and gratitude for all of you , your knowledge, wisdom and kindness. I’m often astounded and delighted at the generosity of human spirit I see here.

What I want to know is, have I got the following straight?

In internal canister filters, HOBs and external canisters we have an little electric motor that, through some voodoo of magnetism and current beyond my reconning, turns a shaft with a magnet, some plastic moulding and a propellor-like blades on it. In the two I have they appear to work by being, in one form or another, adjacent to an otherwise closed pipe/channel which water can occupy, along with the little well that the shaft assembly drops into. This well, by design, not permitting water to pass beyond it.

The application of electricity turns the shaft in one direction which effectively pushes water down one of two available directions of movement, depending on direction of rotation, so the water in that pipe/channel has no choice but to be wafted, like a Mississippi steamer somewhat, or blasted, like a speed boat, in the direction we want.

The system , if both input, to the pump and output, to the tank and filled with water and sit in water we get a, for want of a better phrase, a complete water circuit.

We call the output or return-to-tank side of this the pressure side as pressure from the blades of the impeller forces water in the given direction of flow and in the trailing vacuum created behind it, water is sucked into to replace it in a kind of chicken and egg, push-suck situation, with arguably, the push or pressure side leading and the suck/pull side following as a result.

This flow of water in a confined, airtight space, all else being equal, interrupted by media to cultivate bacteria and the throughput of oxygen-bearing water to feed it, is what we’re calling biological filtration.

I know I’ve used a lot of terms in very loose, unspecific and non-scientific way here so forgive me.

Many thanks

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[LMuhlen]

I'm not sure which parts of your overall description of the workings of a filter you want confirmation on, but it sounds about right. You have a pump, which turns electric power into water pressure by means of electromagetic voodoo and clever duct geometry. The tank and the filter form a closed water circuit which forces oxygen rich water to traverse a bed of media intended for microbial cultivation, and this is where it happens what is referred to as biological filtration.

It is important to note that, despite our best efforts to provide a home for the microbes responsible for "filtering" our water, they tend to grow all around and, sometimes, a poorly planned filter may suffer from low oxygen levels due to a excessively restricted flow and/or too much bacterial activity for too little input oxygen, at which case the filter ends up not being the chosen space for our little friends to grow.

You mention an airtight space, but HOBs are not airtight, at least not in the region past the pump. Not that it matters much, gravity keeps the water in its due place.

As a follow-up, there are those who consider the need for media designed specifically for biological filtration to be unnecessary in a planted tank, as the plants consume ammonia and nitrates and there is plenty of surface area all around for the microbial activity to grow. Proper water flow and oxygenation would suffice for a mature planted tank. As a corollary, looking for "the best media" would be a waste of effort.

 

[dw1305]

Hi all,

Anyway, I’ll dig further on this before removing all my expensive pumice

There is <"nothing wrong with pumice">. If I had some? I'd use it, I just wouldn't pay over the odds for it. <"It is the price">, not <"the product">, that bothers me.

In internal canister filters, HOBs and external canisters we have an little electric motor that, through some voodoo of magnetism and current beyond my reconning, turns a shaft with a magnet, some plastic moulding and a propellor-like blades on it. In the two I have they appear to work by being, in one form or another, adjacent to an otherwise closed pipe/channel which water can occupy, along with the little well that the shaft assembly drops into. This well, by design, not permitting water to pass beyond it.

Yes, that is an impeller pump, it has a <"magnet "spinning" inside the filter head"> and it is that motion that turns the impeller (in its housing) and pumps the water.

We call the output or return-to-tank side of this the pressure side as pressure from the blades of the impeller forces water in the given direction of flow and in the trailing vacuum created behind it, water is sucked into to replace it in a kind of chicken and egg, push-suck situation, with arguably, the push or pressure side leading and the suck/pull side following as a result.

This flow of water in a confined, airtight space, all else being equal, interrupted by media to cultivate bacteria and the throughput of oxygen-bearing water to feed it, is what we’re calling biological filtration.

Yes.

It is important to note that, despite our best efforts to provide a home for the microbes responsible for "filtering" our water, they tend to grow all around and, sometimes, a poorly planned filter may suffer from low oxygen levels due to a excessively restricted flow and/or too much bacterial activity for too little input oxygen, at which case the filter ends up not being the chosen space for our little friends to grow.

and that is the <"potential issue with canister filters">.

You mention an airtight space, but HOBs are not airtight, at least not in the region past the pump. Not that it matters much, gravity keeps the water in its due place.

In the USA they also use wet and dry Bio-Wheel filters (adapted from sewage treatment). You can buy the <"MarineLand Penguin 350 Power Filter"> in the UK, but I've never seen one in operation. I have seen <"rotating contactors"> in sewage treatment works (but not recently).

As a follow-up, there are those who consider the need for media designed specifically for biological filtration to be unnecessary in a planted tank, as the plants consume ammonia and nitrates and there is plenty of surface area all around for the microbial activity to grow. Proper water flow and oxygenation would suffice for a mature planted tank. As a corollary, looking for "the best media" would be a waste of effort.

That is very much where I'm coming from. If I wanted to keep a much heavier fish load I'd be looking at <"planted wet and dry trickle filters">, and I still wouldn't be too worried <"about the media in them">, even if I <"couldn't use Hydroleca">.

cheers Darrel

 

[MichaelJ]

As a follow-up, there are those who consider the need for media designed specifically for biological filtration to be unnecessary in a planted tank, as the plants consume ammonia and nitrates and there is plenty of surface area all around for the microbial activity to grow. Proper water flow and oxygenation would suffice for a mature planted tank. As a corollary, looking for "the best media" would be a waste of effort.

Agreed. I have two mature densely planted 150L tanks and for such I more and more look at my HOBs and internal filters (I have two Tidal 35's in each tank and two small PatMini internal filters to provide extra circulation near the substrate) as a means to create circulation and provide mechanical filtration much rather than biological filtration. While I do still use the Seachem Matrix (biomedia) that came with the HOB filters I do realize the overwhelming part of the biological filtration in these tanks comes from the plants and microbial activity in the substrate.

Cheers,
Michael

 

[Big G]

Thank you all very much.

I was looking to see if my understanding of how an electric impeller pump in a filter assembly works was correct or not.
I completely agree on your reasoning and experience that if our denitrifying bacteria can happily set up shop in pot scrubbers in a filter assembly then almost any surface offering sufficient water flow and oxygen within the tank environment will do too. If that is the case then the dedicated home we offer them is essentially, in a well-planted tank, a backup culture and means of creating healthy flow, no more, no less? (plus mechanical filtration of particulates with high ppi foam and/or filter floss if the aquarist requires it ?)

If this is so it would lead me to think that aesthetics aside, something like a Pat Mini (and similar), say, a sponge filter with a powerhead is about the most effective £ for £ ($ for $) filter for a planted tank. It’s basically a sponge with powered flow.

Similarly, in nano tanks, where space is a premium and one is worried about canister leaks, then at a push a small Eheim Pick Up- style internal cartridge or a HOB filled with cultured media will do the same? (I’ve just ordered a Tidal 35 and currently reading some quite clever, if involved, solutions to it’s known bypass issues)

In a fish only tank, I’m guessing the role of the bioculture in the filter media is more direct as whilst bacteria can set up shop on the substrate too, the incoming ammonia load relative to available denitrifying bacteria is less favourable?

cheers all
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[MichaelJ]

(I’ve just ordered a Tidal 35 and currently reading some quite clever, if involved, solutions to it’s known bypass issues

Please share what that is about? I've owned 4 for years now and haven't had any bypass issues... I am actually not even sure what it means

EDIT: In my shrimp tank I do have a coarse sponge in front of the intake which restricts flow a bit, if that is what you are referring to. In my other tank where I don't have sponges in front of intake I've never had problems with debris getting stuck in there.

Cheers,
Michael

 

[Big G]

Here’s the one I’m thinking of primarily;



The first five minutes is less relevant on the 35 as there’s no inflow pipe but the principle remains largely the same.

I can certainly see where this chap is coming from in that water might, when ‘pushed’, as is the way with this configuration of pump before media, be inclined to take any paths of least resistance by availing itself of the various escape channels that are available to it from about halfway up the media basket (the slits in the back, and the ‘window’ in the front etc) ,rather than negotiate any media actually in the basket to get to the exit spillway thus bypassing the media lower down.

However, I’m sure Seachem did this on purpose based on a worst case scenario of a) flow turned to maximum and b) media remaining unrinsed or neglected for long periods of time. In such a scenario one wants to give water escape channels to avoid input exceeding output to the point of flooding out of the top of the filter onto well, anywhere other than back into the tank.

For example, if the white basket had no holes in the bottom, no window, no bypass slits and no bypass channels behind it, water would simply fill the basket then continue to accumulate to a point where it would be chucking water out of the spillway at the maximum aperture possible and with a powerful pump - that might not potentially be enough, I would speculate. Again, I have no doubt Seachem have balanced power with flow and worst case scenarios to avoid it being all but impossible. There’s just no acconting for that one person that fills the basket with quick drying cement though right?

The fact remains though that for some, and I’m undecided into wether or not I’m one of the ‘some’, any bypass is unacceptable as far as filtration goes.

Provisionally, my inclination would be that ;

a) the folks who designed this have test rigs I can’t replicate easily without lots of money, space and time. They’ll have run tolerance tests.
b) I’m not urgently in need of making sure every molecule of h20 passes through the media every pass and the tank it may go is going to mean at least 8 passes per hour. Volume/ flow rate etc.
c) to assist the water in ’choosing’ the basket rather than the bypass I would be inclined to use less restrictive media so course sponges.
d) I have shrimp too and I would expect that any small enough to not be capable of overcoming the relatively modest draw from the vents will enjoy an impromptu flume ride and be safely flushed through a bypass into the tank again (or rescued when the unit is tipped into a bucket- I check all my waste water for shrimplets when syphoning/water changing before disposing of it anyway. Time consuming? Yes, but I really value my little critters and do my best for them as I happen to be their custodian).
e) if the main use of a filter in a planted tank is to give a reserve battalion of denitrifying bacteria and to provide flow and some turnover/oxygenation, as discussed earlier, I think that’s a win.

Be very interested in what you think

cheers

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[Big G]

Duplicate post. Apologies. I have deleted.

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[dw1305]

Hi all,

If this is so it would lead me to think that aesthetics aside, something like a Pat Mini (and similar), say, a sponge filter with a powerhead is about the most effective £ for £ ($ for $) filter for a planted tank. It’s basically a sponge with powered flow.

<"Exactly that">, but I like a bigger sponge. If I had a fish-house I'd use a <"piston air pump, air ring, Czech air-lifters"> and these (or <"Eck-HMF">) sponge filters.

cheers Darrel

 

[Big G]

So my Tidal 35 arrived this evening and taken it apart to check it out. I have to say ; in terms of build quality I’m impressed. One important point though, on close inspection of the flowpath I can see that MichaelJ is TOTALLY right about putting some coarse sponge across the inlet grills (main and skim). There’s no way a little shrimp isn’t going risk getting macerated because of the flow path in this configuration.
Aside from that it seems a really nice, solid bit of kit. I’ll test it over the weekend for noise, bypass etc.

cheers

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