How often do you change/clean your filter sponges on a external filter?

[Marne]

Some people seem to clean there's once every 3-4 months, some once a month and some every week, how often does it really need doing?

I have just had to do mine after my tank started smelling odd ( like onion ), apparently it's due to the filter being dirty ( according to google ) so I checked my filter and it was quite rancid, I only cleaned it 8 weeks a go but I'm now thinking I need to do it a lot more often?

There are too many variables to say a set time- it depends on how many fish you have and what species, how much they eat and what sort of food, whether you have lots of feathery plants, etc etc etc.

So trial and error is the way to go. The aim is to keep the water flowing and to not have loads of crap in there breaking down and adding to the ammonia level. Every 3-4 months isn't very often, so that would be for a very lightly stocked tank with titchy, tidy fish.

I used to do mine once a fortnight for goldfish and once a month for a tropical community. If it was rancid then you defo need to do it more often. I've never heard of the onion smell but it doesn't sound good all the filth knocking around can harbour dodgy bacteria and cause fish deaths.

I panicked when I smelt it ( was fine a couple days ago ) so googled, apparently it happens when you don't have carbon in the filter ( I took mine out when I treated the tank a few weeks a go ) and when it gets dirty, I have around 25 fish in my tank at the moment, most are young guppies, a few Corys, a very young shark and my bn plecs ( these do poop a lot ), tank is 200ltr, I do a 30% water change every week ( sometimes I change closer to 50% ), water is always clear unless I'm a day or two late doing a water change. I have put the carbon back in and rinsed the sponges, will now do it every couple of weeks, hopefully the smell will now go, if not I will do a big water change tomorrow.

You don't need carbon if you stock and clean your tank properly. It needs replacing every 4 weeks so gets expensive. Just clean your filter more often and it should be fine. I wouldn't rely on google for fish information, there's some utter bullshit out there. Join a decent fish forum and ask on there. Or ask on here

Thanks Eau, I will just step up the cleaning, I have also had a problem with black beard algae ( I think that's what it's called ) and I have removed most of my bog wood as it seemed to be growing on there and is a nightmare to scrub off ), I think I have got rid of most of it, is there any way to stop it coming back or is there a fish that would eat it?

Oh, it's a bugger to get rid of. Stuff your tank full of fast growing plants and use liquid carbon, that should keep it under control at least.

What's your phosphate level?

A lot of people say that siamese algae eaters eat BBA but I wouldn't add one, you've already got a shark and you've got smaller fish that the SAE would pick on. Control is the best option, rather than eradication.

Not sure what my phosphate level is. I don't have any real plants in my tank at the moment but I will get some, it seems to grow on my bog wood and around my heater, it's a nightmare to scrub off, I will try some liquid carbon.