Illustrated Guide to Reusing a Disposable Aquarium Filter




This is my first instructable and is intended to compliment pixelinabitmap's "Cheap Filtration For A Small Aquarium instructable. This is not intended as a replacement, as his instructable gives a much more thorough explanation of the processes at work. However my instructable adds photos of the process and a couple of minor modifications I made to his original description.

The idea here is to purchase a cheap disposable filter (around $3 or $4) and reuse it by recharging the carbon and zeolite yourself. This is much cheaper then buying a new disposable filter each time you need a new one. Note that these filters are recommended for small aquariums or fish bowls, so you won't want to use this on your big 55 gallon tank.

Things you'll need:

  • Disposable filter (at most pet stores for around $3)
  • Air pump, the smaller the better. Mine was only about $5 at the pet shop
  • Air stones - these make the thing way quiter. I think it was $1.99 for a two pack and these will have to be replaced every so often.
  • Activated carbon, this is about $3 or $4 for a big container of it at the pet store.

Step 1: The Discard-A-Filter

I recommend doing this modification before using the filter (as opposed to using the filter for a few weeks and then disassembling it when you're ready to replace the contents). I bought a two-pack of these and the first one I modded without a hitch, but the second one I had been using in the bowl and it made the plastic too fragile so it started breaking in places I didn't want it to (and not breaking in places I did want it to).

Step 2: Disassembling the Discard-A-Filter

First, remove the clear plastic grate from the top. The easiest way to do this is to start at the top and use a utility knife to cut away the glue that's holding it in place.

Dump out the carbon/zeolite and remove sponge.

Pull out the blue plastic grate. When I did this on the first one it popped out no problem, but when I tried it with the wet one, it broke off.

Step 3: The Modifications

On the back of the filter is a clear tube attached to a blue square which is glued into the back. You'll want to remove this piece. Your best bet is twisting it out with a pair of pliers.

I left the top suction cup in place, and pulled out the bottom one. To block the hole left by the bottom where we pulled out the air hose, I cut the cup part off of one of the suction cups and plugged it back in.

Pull your air hose through the top hole and attach an air stone to the end. The air stone will make your bowl virtually silent, whereas without it, it will be quite loud.

Cut out the bottom 6 or 7 grate pieces, just enough space to allow the air stone to poke through. Now that you've done this the hole blue part will fit back in place the way it was before.

Step 4: Recharging the Filter

Place the sponge back in place. The sponge holds good bacteria that converts ammonia to nitrites to nitrates. If it gets filled with large debris, you might try just swishing it in some dechlorinated tap water to get the larger bits out and then putting it back in. It should last you a while, after which you can just pick up some filter media in bulk to replace it with but doing this may "recycle" your tank (get rid of most of the good bacteria) so you may want to plan accordingly.

Refill the carbon and zeolite into the top portion.

Replace the clear plastic grate on top and fix it to the body with something. The original instructable suggested rubber bands, I used a long sandwich bag tie.

Rinse the filter out under in some clean water to clear out the carbon dust and you're all done!



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    14 Discussions


    7 years ago on Introduction

    I see a number of things here which make me think that there are a lot of people new to aquaria reading this, so I thought I add 2c worth on aquaria since I learnt the hard way.

    Here's a great article on activated carbon you need to read:

    And the floss works as a filter by a) trapping particles and b) using good bacteria to convert the extremely poisonous fish piss into nitrates, which can then be rid of with partial water changes. This is 90% of the solution in keeping things clean. Thereore, ALWAYS ONLY RINSE YOUR FILTER FLOSS IN USED AQUARIUM WATER, NEVER in tap water!!! Don't add fresh untreated tap water into the tank either.

    Speaking from experience, after setting up your tank, there is 1 very important but simple basic rule on keeping your fish healthy:

    HANDS OFF! Don't rock the boat! Never do anything lots or fast. Don't fiddle! The ecological balance, like a see-saw, can be disturbed very easily, and when it falls over, it can fall fast, and you will lose a lot of fish.


    1a) DON'T CHANGE TOO MUCH WATER. Except for emergencies (where you KNOW what you are doing!!!), don't change more than 30% of the water at a time. Don't change any amount of water more often than twice a week, or less often than once a month. Use the same source of water every time.
    20-25% once a week is probably around the ideal. This takes out the nitrates, which otherwise will build up.

    1b) DON'T FEED WHENEVER THEY LOOK HUNGRY. Don't feed a lot or often, even if they ask you, until you have had them for at least a month and also know what you are doing. Feed just a little. A hungry fish will be a litle thinner than normal and has something to do: look for foood. A WELL-FED FISH WILL DIE OF FUNGUS. If you know what you are doing, feed just a tiny bit morning and evening, otherwise, just mornings is probably safer. If things have gone wrong, once a week. The fish will handle this just fine for a few weeks. Feed food that does not disintegrate fine particles that fall into the gravel and decompose, adding microscopic fungus to the water. If they eat it all up in a minute, you are underfeeding. If there is some left after 5 minutes, you may be overfeeding. Let them be hungry enough to search for food, it;s all they have to live for. Don't let them get bored being overfed. They will die, I promise you.

    1c) DON'T ADD LOTS OF FISH. Just a couple a week, so that the filter bacteria cvan grow up to handle their waste. (And check beforehand which kind of fish can go together! And some fish are unhappy and stressed out if not kept in a school of 5 or 6 [so add 3 at a time, or 5 small ones]. And some need space not friends, like Paradise or Siamese.) And understock your tank - this will pay off. You can rather get to know your fish which you do have, as friends. They do learn to relate, you know.

    1d) Keep soaps and soap-washed things (incl hands) and anything else you can think of including fresh untreated tap water away from them, and away from the filter!

    1e) Don't spring clean your tank or filter media. When you must clean, pick one thing at a time, or half your filter media, and clean it in used aquarium water, to keep the good bacteria on. (BTW these good guys cover themselves with a slimy film you can feel but not see - this is not a bad thing, it is a good thing.) Use a gravel washer to clean a different part of your gravel at a time. This changes the aeration of the gravel, which can release sulfides if the gravel is deep enough. Don't go deeper than 4 cm.

    1f) If fish do get sick, don't panic and add all kinds of medicines or change everything. First off, i) Get skilled advice. Diagnose very carefully. and ii) Stop feeding till you have diagnosed accurately, and possibly longer. and iii) Change 20% of the water.

    Just watch the fishies! :-)


    10 years ago on Introduction

    Additionally, you shouldn't buy any more of those plants. Looks like it's Mondo Grass and it can't survive long-term submersion in water. If you do decide to get plants for your tank, make sure you avoid these, Lucky Bamboo, and another type of variegated and non-variegated Dracaena.

    2 replies

    Reply 9 years ago on Introduction

    I use Lucky Bamboo in an open-top 6G aquarium with laterite as a substrate. It is beautiful and the plants LOVE it as long as their tops are out of the water. They are a very deep green and grow quite well.


    Reply 9 years ago on Introduction

     Oh, I agree. As long as the stalks are out of the water, the plant will do fine. But the other aforementioned plants will just rot completely. I've even seen coconuts being offered as aquatic plants. 

    Another cool plant that can survive in the water (so long as the head of the stalks remain above it) is the Umbrella Palm (cyperus alternifolius). Its root system can overtake your soil if left unchecked, though. :)


    Reply 10 years ago on Introduction

    This baking just removes the organic elements. Any metals absorbed will still remain.

    These days carbon is no longer required in most peoples aquariums.
    It's often just a filter manufacturers plan to get you to buy more from them every month.

    It's a hang-over from the 1970s.

    AC needs to be changed every 3 days. Not every 2-3 weeks. ;-)
    Manufacturers don't like telling you that...


    10 years ago on Introduction

    Congratulations. You just removed almost all traces of nitrifying bacteria from your tank! I hope you like doing frequent large water changes for the next 3 weeks so your bacteria colony can re establish itself, or your fish could suffer from ammonia, and nitrite poisoning! Tip: Get an actual filter.

    5 replies

    Your nitrifying bacteria (Nitrosomanas Marina, Nitrospira spp., and Nitrobacter) need water movment, aeration, and exposure to Ammonia/Nitrite to survive. The best place for this is in the filter. In your case, the floss holds your nitrifying bacteria. By rinsing it, (In non-dechlorinated water) you kill the bacteria almost instantly. If you replace the floss, you get rid of the vast majority of your bacteria. Sure, there is some bacteria in the gravel, and on decor, and even the glass, but not much. Not much at all. You should think about getting an actual tank. That way, you can get a proper filter that will actually filter efficently, as opposed to the obsolete uplift tube designs.

    Thanks, I appreciate the information. I've updated the instructable accordingly. I would like to get an actual tank eventually but right now I'm working with what I have.

    Understandable. As long as you plan on upgrading in the near future, you shouldn't have a problem. If you have any questions shoot me a PM.

    The floss is just a base for the bacteria, whatever to live in and they decompose material in the water. Its not really a filter. In a well balanced tank you can get by with just 1/3 water changes monthly. I used to just rinse my floss out and put it back in 'dirty' with the larger material rinsed out.