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Pre-filters

idris

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3 Jan 2011
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In reviewing my filtration, I keep reading about pre-filters.
I don't currently use them.
As I understand it, they are basically just a piece of coarse sponge over the intake of a canister filter.

I've also read quite a few recommendations about cleaning pre-filters regularly, whilst cleaning the media in a canister less often, so as to not disturb the bacteria. This may be valid, but I'm sceptical about the need to mollycoddle bacteria: if the media doesn't dry out and is only washed in tank water, that seems sufficient to me.
Additionally, I've seen comments from UKAPS gurus, that moving organic waste from the tank to the canister still keeps it in the water column ... which makes a lot of sense to me.

So other than convenience, are there any advantages to pre-filters?
 

dw1305

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Hi all,
I've also read quite a few recommendations about cleaning pre-filters regularly, whilst cleaning the media in a canister less often, so as to not disturb the bacteria.
It is not so much a microbial issue for me, it is more that it saves both time and <"wear and tear"> on the gaskets etc of the filter.

I like filter media that is, to some extent, <"self cleaning">, and I would guess that the filters would carry on with reasonable flow and the filter media <"all aerobic pretty much eternally"> without any <"intervention on my behalf">.
As I understand it, they are basically just a piece of coarse sponge over the intake of a canister filter.
Yes, <"Eheim sell a modular one">, or you can use a big sponge block. I like the drilled <"sponge blocks they sell for Koi ponds">. Swiss Tropicals in the USA <"sell a similar design"> for use with an air pump etc.

A <"big pre-filter sponge"> just means that it is much less likely to clog and you can go longer between cleaning intervals, if <"life intervenes">,

The main thing the pre-filter does is keep all the <"mechanical filtration out of the filter body">. I just want oxygen and ammonia entering the filter, I definitely don't want it to <"work as a syphon">.

cheers Darrel
 
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idris

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In my ill conceived set up, the convenience of cleaning a canister vs in-tank pre-filter is not as clear cut as it might be for others. #ifIdKnownWhatIKnowNow
 

tam

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Yep, my 'filter clean' is just pulling the sponges off the intake and squeezing them out in a bucket of water when I'm water changing. The filter hardly ever gets touched. It's just so quick and easy.
 

dw1305

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Hi all,
In my ill conceived set up, the convenience of cleaning a canister vs in-tank pre-filter is not as clear cut as it might be for others
Yes it doesn't matter where the mechanical filtration media is if you are very conscientious about changing filter floss, or squeezing out fine sponge, from the filter body, it is just that I <"know I'm not">.
my 'filter clean' is just pulling the sponges off the intake and squeezing them out in a bucket of water when I'm water changing. The filter hardly ever gets touched. It's just so quick and easy.
That is it for me as well, quick and easy, it just means you are much more likely to <"do it every week">.

cheers Darrel
 
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erwin123

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Singapore
I used to have a small pre-filter sponge over my Lily pipe intake because I thought I needed to protect my shrimp. My tank has a lot of stem plants that shed leaves, and these leaves slowly accumulated on the sponge pre-filter.

In the end, I found it simpler to let the leaves get sucked into the canister, because the size of the Fluval 307/407 pre-filter compartment is huge and can go for months without being clogged, compared to a small sponge on the filter intake of a 1000/l hr canister. And after several months, I've only found 1 shrimp in the canister so far, so the intake wasn't actually a shrimp magnet.

I have excess filtration capacity for my tank so I can sacrifice some flow rate to do mechanical filtration using fine sponges/polishing pads etc, but my media trays are not that full as i have removed most of my Matrix/3DM "bio media".

From my experience, fine sponges don't clog up that fast. Before the water hits the fine sponges in my canister, it has to pass through the coarse pre-filter sponge, and two layers of medium sponge which should trap most of the larger particles, leaving the fine sponge to do its job of removing the remaining small amount of fine particles in the water. I don't know what the ppi of my sponges are but ideally I would want to an arrangement like 20ppi (prefilter) -> 30ppi (medium) -> 40ppi (medium) -> 50ppi (fine).
 

dw1305

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Hi all,
Additionally, I've seen comments from UKAPS gurus, that moving organic waste from the tank to the canister still keeps it in the water column ... which makes a lot of sense to me.
Which would be one reason I wouldn't ideally use @erwin123 technique.
to let the leaves get sucked into the canister, because the size of the Fluval 307/407 pre-filter compartment is huge and can go for months without being clogged, compared to a small sponge on the filter intake of a 1000/l hr canister.
I have <"snails and Asellus"> in my filters, partially because they will shred any woody debris that makes it into the filter (Cherry Shrimp would also perform this function).

Snails eating the nitrifying biofilm at sewage treatment plants is a known problem, so probably not ideal for <"non-planted tank keepers"> who are more reliant on microbial filtration.

cheers Darrel
 

Oldguy

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27 Aug 2018
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Gloucestershire, UK
pre-filters
I use the tank's inert substrate as a pre-filter ie under gravel filtration. For high turnover CO2 distribution I use fine stainless steel cylinders as pre-filters to the circulation pumps, the type used to keep shrimp from being sucked into filtration systems.
Water column water also passes through an external 'dry' filter which is not a filter in reality but an oxidation tower.
Each to their own, it all depends on space available. and ease of access to the tank for maintenance.
 

idris

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Water column water also passes through an external 'dry' filter which is not a filter in reality but an oxidation tower.
Cam you elaborate on this please?
 

Oldguy

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Gloucestershire, UK
Cam you elaborate on this please?
Part of the system is an external canister, the feed is via the under gravel uplift and the return is divided. Part of the return flow is through a UV unit and part of the return flow is via an old angle iron aquarium. I welded lugs to the frame and glazed it so it was vertical and mounted it to a wall above the display tank. Water enters via spray nozzles at the top and drains over fired clay balls and out of the bottom of the unit and back into the display tank. This gives a good exposure to air of water trickling down the balls in the unit, hence I regard it as an oxidation tower. The unit runs 24/7

The display tank is set into a chimney and is viewed from one room but all the gubbins are in a cupboard in another room out of sight.

I hope this is of help.
 

idris

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I'm impressed just reading that, and that's before I've even had a chance to process the information and picture it!
 
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