Prefilter yes or no?

[-carlo]

I've been reading about sponge pre filters and can't quite figure out why or why not.

Currently I don't have one but my canister filter gets dirty quickly. I clean it every two weeks to a month. A lot of pleco poop gets sucked up but I siphon the tank at least once a week to get the rest. With a pre filter I presume you clean the canister filter less. But will you still get most of the poop out of the tank?

Do you have a pre filter? Why or why not?

[TwoTankAmin]

This is not a simple issue. The purpose of a pre-filter is to prevent the larger particles from entering the filter. The reason for this is simple. Clogging/blocking flow is the enemy of filtration. When it comes to pumps and filters, it is always a bad idea to limit flow on the intake side rather than the return side. This is what breaks the mechanism.

So for a pref-filter to work well there are two considerations. How porous is it and how often is it cleaned. Pre-filters should be made from fairly course foam. The finer the porosity, the faster it will clog. And once clogged there can be damage to the mechanical side as well as a loss of filtration capacity. Porosity is measure in pores per inch, PPI. and you want to shoot for a low number.

I have used pre-filters on powerheads, hang-ons and canisters for many years now. My rule is they all must be rinsed weekly to prevent clogging. I learned early on that failure to clean is a recipe for disaster. If you have ever seen a sponge filter that is collapsed around the center frame, you have seen what happens when you do not clean sponges. But with air driven you will only lose filtration but will not damage your air pump. With mechanical flow driver, blocking the intake will overheat them and likely break them.

I have normally only cleaned my 3 canisters twice a year. However, on one I use exclusively Poret foam. This canister has now been running for over two years without being opened. I was told that it is time to clean it when I can see the return flow slowing. I am still waiting. This tank has another filter and lots of plants. Both filters use pre-filtering. It is also currently grossly overstocked.

As for what I use as pre-filters:
- ATI Filter Max III http://www.kensfish.com/aquarium-suppli ... max-3.html
- The foam used in an AquaClear 110/500. The bigger the AquaClear, the coarser the foam (lower the ppi). I cut it to size.
- Poret foam 10 ppi

I hope this helps.

[-carlo]

Very thorough and helpful. Thank you.

I think I'll get a pre filter for my eheim pro 3. I'll just clean it during every water change (every week).

[Bas Pels]

Rinsing a filter every fortnight is plainly too much, so some measure should be taken. An Eheim pro 3 is quite a large filter, but still, not intended for a tak over 1000 liters. Unfortunately, Eheim just does not make large canisters.

And if the tank is heavily populated, or populated with fish making al arge mess, the 1000 liters can easily be reduced to 500 or less

That is, either you should need a second, or perhaps even a third canister, or you should do something to trap the pleco poop before entering the canister. A pre filter does sound nicely, but the woodpulp in this poop is rather fine -close to half a millimeter or smaller. That is, a coarse prefilter will not stop much of it.

I wonder whether the prefilter will help you.

Personally, I stopped using canisters myself. I have internal filters in my tanks, with matten - only matten - and a relatively slow watermovement through them.

then you'll find an airlift, a small electrical pump or even a big one - pumping over 3000 liters an hour. But the matten passing this amount are 60 * 30 cm large

Works really nice

[bekateen]

I've been using foam prefilters on all of my HOBs, but I must confess I've had several disasters, three in the last year, when either I had to skip a prefilter rinse because of heavier than normal work loads at my job or because the prefilters clogged prematurely for some other reason. I've lost four clutches of fry (2 clutches of L397, 1 clutch of Peckoltia compta, and 1 clutch of L201 big spot) as well as a lot of adults (L201 big spot, Centromochlus perigiae, Panaqolus albivermis, Panaqolus maccus, and Hypancistrus debilittera). All of these tanks had in common the presence of Panaqolus in them, so the excess poop production has been an obvious complication.

I admit that finding the proper pore size foam (coarse is better in my view) is key to a good prefilter, I'm actually recoiling away from that in some tanks and removing the prefilter. My filter intakes have never clogged (yet) in absence of a prefilter, so I'd rather have the filter keep flowing with a clogged filter cartridge (no filtration is occurring, but water circulation is continuing) than stop water flow and kill the fish.

I'm also considering moving most of my tanks to Matten filters or Poret cube filters to reduce the risk of such catastrophic clogs, since air driven systems still move air and water. In my larger tanks, I'm considering combining an air-driven system with something like a canister; I do prefer to have two systems in each tank so that if one has issues the other keeps water moving.

Good luck,
Eric

[-carlo]

@Bas
Thanks for the input. I'll do some research on mattenfilters.
I think I should have specified a bit. My tank is 80x45x45cm (about 160l) and my filter has a 950l/h flow (says eheim). On top of this there is a small powerhead installed.
I have 5 peckoltia braueri L121, who are producing most of the poop. I clean the filter often because I know poop builds up there but the flow doesnt reduce. I could probably go for months without cleaning it but I think it would affect water conditions.

@Eric
That is very good to know, I'm not so sure about sponge prefilters now.

What I completely forgot is that my canister has a "prefilter" inside. It is a separate section with a coarse sponge through which all the water flows first, before entering the rest of the filter. This part is easy to clean without disturbing the rest of the filter (Or at least it should be, but mine is broken). I have been delaying with sending the filter to eheim because it still works. But I found the warranty and have an extra internal filter so I will send it for repairs ASAP now.

[dw1305]

Hi all,

......That is very good to know, I'm not so sure about sponge prefilters now.

I'm a fan of matten filters as well, but I like a pre-filter on any external/HOB or Powerhead filter.

I use a really sizeable PPI10, or PPI20, sponge block.

The ones I use are the 30cm x 10cm x 10cm drilled sponge blocks they use for Koi ponds (https://www.ketteringkoi.com/pond-filter-foam-block/), they are drilled 3/4 of the way down to the bottom.

If Poret foam was easier to get in the UK I would use that for preference.

cheers Darrel

[MChambers]

I use sponge prefilters on my canisters. Like TwoTankAdmin said, use coarse foam and clean it frequently.

I’ve converted most of my tanks to mattenfilters, though. You do need to watch those, though, even if driven by air. The lifters can get clogged, very occasionally. Also, I’ve had some mulm build up behind the mattenfilters. I’ve begun using a turkey baster to draw that out.

[racoll]

Prefilters are great. Since using one I've never looked back. Really improves the performance of the canister filter in my opinion, and saves a lot cleaning effort.

I think as long as it becomes part of the weekly tank maintenance, I don't think clogging will be too much of an issue. It's a good idea to have the canister outlet above the water level so any drop in flow can be easily observed every day.