How to Clean your Filter

There’s a tonne of information out there on tank maintenance and fish keeping but very little that specifically addresses the correct way to clean your filter out WITHOUT killing all the friendly bacteria in it and so prompting a mini-cycle.

I’ve had friends and people on this blog contact me several times over the past couple of years complaining that all their fish have suddenly died for no reason.  I need to make something clear right now healthy fish do NOT suddenly all die for no reason,  the problem seems to be that people don’t associate their actions with the reason for the fish death.

The best line came from one of my friends “Well I look after my tank and clean the filter weekly so there’s no reason for the fish to die”.  After further digging it turned out he didn’t like the fact the sponges had changed from white to a mucky brown colour so he decided to bleach them and rinse them under the cold tap.  He’s not alone in this my mother of all people insists on putting new filter sponges in her filter every time she cleans it out!  I’ve actually given up on trying to teach her the proper method of filter cleaning.  Hopefully this simple bit of advice will help you all avoid the issues others have faced.

There is one main simple rule to follow and doing this one thing alone will save your fishes life.

Only ever clean your filter in tank water!

I follow this simple process.

  • Half fill a bucket with tank water.
  • Take filter out of tank if internal / If external isolate the hoses and disconnect it from the tank (leaving the hoses full of water this saves you having to reprime your system)
  • Take bucket + filter over to sink (it helps to put the internal filter in the bucket save you dripping on the floor)
  • Take filter apart in sink pour filter water away and put sponges/filter media in your half full bucket.
  • Clean filter housing / plastic under normal tap water clean out the impeller and remove any crap build up.
  • Solid filter media alphagrog /K2 / ceramic rings give a quick mix about in the half bucket then put back in filter DO NOT clean it under tap water.
  • Give your sponges a good squeeze and rub together in your half bucket of water.  Now at this stage the water will be filthy and your sponges may not be clean yet.  Pour that half bucket away and get another fresh half bucket of tank water from your tank!
  • Repeat above process again for sponges.  By now they should be clean.
  • Put filters back together.
  • Take back to your tank, connect up and turn on.

Your filter is now clean and working again, you’ve not killed any of the friendly bacteria off of it and you won’t experience a mini-cycle.  If your sponges are knackered and do need replacing do NOT replace them all at once.  Clean the filter as above change half of the sponges this clean and next clean change the other half.  This will ensure your new sponges are populated with bacteria asap and again avoid a mini-cycle.

At this time you’ve also conveniently removed a bucket or perhaps more of your tank water so you can top up using fresh water and now you have done your weekly water change all at the same time.

It really is as simple as that to keep your filter healthy.

Red tailed black sharks rediscovered in the wild

It seems that one of my favorite fish the red tailed black shark which was until recently thought extinct in the wild has been rediscovered.  While its still too early to say its a full recovery of population the fact they’ve been observed at all is amazing.

You can go read the article over on practical fish keeping which also has a linked PDF report from the scientists who have observed the fish.

Reader Questions: What to do with pest snails

Hi. I have had a tank for over a year & have had no bother with it , but about 6 weeks ago I put a live plant in along with my artificial ones & now I’m plagued with baby snails. Is there anything I can do to get rid of them, I squash as much as I can but back they come, hope you can help Geo. { I,ve removed the plant}


Easiest way is to put in some fish that eat snails, the obvious ones that spring to mind are YoYo loaches.  Another alternative would be assassin snails although as I found my assassins seem more interested in eating each other than the pest snails.

You can also use a snail trap to harvest them.  Get a small mouthed bottle (something your fish wont fit in) put some lettuce leaf inside it and sink it into the water over night.  Pull it out the next day remove empty the bottlefull of snails you have and repeat.

Readers Questions: How do I stop a powerful filter disturbing my substrate

Dave couldnt get a eheim powerball but been advised aqua one 102f is next best thing for my 64l tank ive put it just under the water level kept other filter in coz of keeping bacteria levels up turned it on and omg cant tell u how its kicking up the sand etc. Ive turned it off at mo cant see the fish …. will it be ok shall i just run it to see how it clears it says suitable for up to 70l


Just ignoring the specifics for a minute and looking at the main problem there are several ways you can address the issue of a powerful filter disturbing the substrate in your tank.

Rule of thumb here is to point the water jets or outlet from the filter towards the surface.  Now in most externals this is easy, use a spraybar on the output and twist it so its pointing up and across the tank kinda diagonally, don’t point it directly so it’ll come out of the surface otherwise you’re going to get very wet.  Put the outlet and one end and have it spraying full length of the tank.

With internal filters its a little more difficult not every filter comes with a spraybar.  The thing to remember here is that filters don’t have to be upright to work! By that I mean you can have your filter horizontal across one end of the tank or on a diagonal which should give you a measure of targeting to  get the filter outlet aiming away from the bottom.  Some filters also come with left right horizontal adjustment on their outlet, once the filter is on its size suddenly left right becomes vertical up down so you can really target the water flow up wards.

Other usually more expensive (though not a requirement by any means) internal filters come with a flow rate adjuster so you can turn the flow down an example of this would be the TetraTek IN range of internal filters.

aqua one 102f

In this specific case the Aqua One 102F comes with a spraybar attachment instead of an outlet simply turn it so the jets are pointing slightly upwards and along the length of the tank and you should be fine with no more disturbance in the substrate.  Now there is a little caveat to that if the tank isn’t very wide the spraybar may still be too powerful as by decreasing the size of the output holes it increases the speed of the water flow!

You can change the output again to the wide open end making sure to use the venturi pipe (letting in air via the venturi also slows the flow down) as above lay the filter horizontal and use the twist action of the output to point it upwards and across the tank.  Don’t be afraid to lay the filter near the bottom of the tank either there’s no rule that says the output needs to be at the top!

Readers Questions: Lighting advice for a new keeper

hi i am a new to fish keeping , i have got 8 fish in my tank got 6 tetras 2 zebra danois wanted to know as the fish live in the tank can i switch off the lights to give them a rest then put it on in the morning will this make a diffrence to them

First up no the fish don’t depend on the light at all with a few exceptions they’d be perfectly happy with just the natural sunlight they get.  Unless you run a heavily planted tank I’d only leave your lights on for a max of 3-4 hours in an evening when it gets darker.  If you run them all day/night not only is it costing you a fortune in energy but the fish are getting no rest period ie: night and you’re massively increasing your chances of having to deal with green water or an algae bloom.

Rule of thumb don’t turn the lights on before 5pm :) and turn them off by 10pm.  I have mine on timers to achieve this.

Update on last Reader Question

Update: today Andy is not doing well. All of her fines are frailed at the end and she has lots of red under her skin. She is not moving around at all and breathing abnormally.

Unfortunately as before there’s not much you can do just make sure the water is in top quality its well oxygenated. May be worth while sticking a couple of airstones in if you can to increase surface movement and oxygen levels.

There’s no real potions or lotions you can use for this and to be honest 99% of them don’t work anyway. All you can do is sit back and wait. If it looks like she’s being bullied you could remove the bullying fish or move her to a holding tank on her own for a while (although this may further stress her) but apart from that sit back and keep your fingers crossed.

Another TV show looking for kids and their pets

Name: Richard Hunt
Comment: Hi,

Hope this email finds you well,

I’m currently working for the Disney Channel on a new kids TV series called Furry
Friends. Each 3 minute episode will look at a child and their relationship with
their pet.

We’re looking to cast a 4-7 year old who is a great little character along with
their pet Fish. We will look at their daily routine showing the care and
responsibility of having an animal as well as all the fun that goes with it.

I wondered if you either knew of any young families who might be interested in
taking part, or if you are able to post something to your website. If you are I’d be
most grateful of you passing on my details – 0208 222 5935 or

Many thanks for your time and help.


0208 222 5935