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should i ever clean a sponge filter?

Ben Rhau

Hi all,

I've reading some advice that appears to be conflicting.

1. Stephen Tanner's article on biofiltration implies that one should rarely, if ever, clean a filter. This tracks with the design of the Mattenfilter, which looks damn near impossible to clean without disassembling the tank setup.

2. Others say that, particularly when fry are present, vacuuming the substrate and cleaning the filter reduces BOD.

I was raised only thinking about biofiltration, and indeed never see ammonia or nitrite in my tank (as far as I can tell from imperfect water testing kits). My tank is understocked and heavily planted, including with floating plants, so my nitrates are always low. The adults are happy and spawn like clockwork. However, I so far do not have a great fry survival rate. I am wondering if a contributing factor is that my BOD may have become too high with fry, fry death, and fry feeding.

The next time I see one of my females brooding, I'm thinking I should squeeze out my sponge filter and keep it clean once I see the fry. Today, I cleaned it for the first time in 3 months. Is this recommended? How often do you typically clean a sponge, and how does this change when you have fry?


Mike Wise

Staff member
5 Year Member
I do the same as Ben Rhau every time I need to break down a tank where I can't catch the fish otherwise. That means I do it rarely; maybe every 6 months to a year. I also have tanks with sponge filters that I can't remember when I last cleaned them, other than putting a siphon tube to parts of the sponge and sucking out some gunk.

Ben Rhau

OK that helps. In that case I will focus on aggression/predation. which seems the mostly likely reason I'm losing fry, given the circumstances.


Well-Known Member
5 Year Member
Hi all,
How do you clean your sponge filter? Squeezing out excess crud ok. Rinsing in dechlorinated water ok.
I don't tend to squeeze them. We have lightly chlorinated water, so I just leave them with the tap running on them in a bowl. Pour off the cruddy water (through a net to retrieve all the Asellus & Crangonyx) and then give the sponges a good swirl in some rain-water, and put them back in the tank.

cheers Darrel


I run 30 tanks and clean sponge filters perhaps twice a year. It is usually when I think the flow has been cut down by particles trapped in the filter. When I do the next water change I fill 2 buckets with tank water. I take the filter out as delicately as possible being careful not to squeeze it or allow too much water from it back into the tank. Squeeze the filter out in bucket 1 and then in bucket 2 (you'll be amazed what comes out), reassemble and back into the tank. Our city water is heavily chlorinated water, I don't want to kill the bacteria needed in the filter. There is thinking that a well aged tank can repopulate the filter with bacteria easily but this is just the way I was taught, for what it's worth.


I clean them with every water change: reason being: 1. Toomuch detritus may block up surface area for bacteria and more importantly 2. Sometimes the air flow reduces and whilst this may be more to do with the non foamy bits I blow through the iar hose and give the sponge a quick squeeze in removed water change water. In any case there should be heaps of bacteria left and I have never suffered any adverse events. I find that sponges do collect quite a bit of detritus and in the abscence of any mechanical filtration I want to remove this where practical.