If you have a waterfall (hang-on-back) style aquarium filter and you would like to upgrade it to a canister filter, you are in luck. There main advantage to a canister filter is that it can hold more media - but then what to you do with your old filter? Why not just convert it?
Step 1: Gather Your Materials.
Everything you need is probably available at your local dollar store. You should get:
1. Two Sections of hose (or one long section you can cut)
2. Some sort of water proof epoxy for sealing (Recommend plumbing epoxy putty)
3. Two female hose quick connects ("TapSpray Nozzle Connector")
4. Two male hose quick-connect joiners ("2-Way Snap-In coupling")
5. Something to use as filter media (Zeolite, filter floss, etc.)
6. Some kind of water tight plastic storage container (Screw together or with latches).
7. A cheap soldering iron (You could potentially use an awl and some kind of files instead)
We are also using your existing pump from your waterfall (hang-on-back) filter for this project. If you don't have one but you still want to do this project, you can buy a power-head and it will still be cheaper than buying a pre-assembled filter.
Step 2: Make Holes in Your Container
You will need to make two holes in the top of container big enough to push the hose quick connect joiners into, until they stop flush.
If you don't want to invest in fancy drilling equipment and you don't have files on hand, a cheap soldering iron works just fine to melt the holes.
Tip: Keep trying to fit the connectors in as you make the hole larger little by little, so that you don't make the holes too big!
Also, make sure the holes are far enough apart, as the female quick-connect plugs will have to fit as well eventually. When you are done, your container should look something like the second photo.
Bear in mind that the holes don't have to be perfectly round since we'll be sealing them anyway.
Step 3: Fit the Connectors to the Container With Epoxy
Make one last check to make sure that the connectors (labeled as "2-Way snap-In Coupling" on the packaging) it into the holes you created, but the flat area sits flush against the surface of the lid. Make sure the flat part of the connectors is on the TOP of the container, as if not, then you won't be able to connect the hose later.
Take out your plumbing epoxy and start mixing it. (It is recommended to wear gloves).
It is recommended to rough up the area of the container to be sealed using fine grit sand-paper or similar. While that probably isn't necessary, make sure the top of the container is near to flush and break off any protruding plastic left over from your soldering iron adventures.
First, the top. Make a thin roll and put the epoxy around the bottom of the connector, before pressing the connector against the container. You should use enough epoxy so that it seals the cracks, and a small amount comes out the bottom. Repeat this for the second connector. I used about 20-30% of the epoxy on the top.
Next, the bottom. Apply liberally and press hard to make sure you fill in any possibly way for water to come through.
The timing will vary, however the epoxy I used set in 1 minute (so you have to be fast!), and cures completely in 60 minutes.
Step 4: Fit the Connectors to the Hose
Unscrew the female quick-connects (Labeled "Tap/Spray Nozzle Connector" in the photo) and insert the hose before screwing tight again.
Once the epoxy on the container has cured, you can try connecting and disconnecting the hose to the new filter. It should make a clicking sound when connected properly.
Step 5: Add Some Hose for the Inside
In order to make water actually go through the filter media instead of just taking the shortest possible path, you have two options:
1. Use some extra hose to make the entrance and exit on opposite sides of the container.
The tricky part about this is that the hose has to penetrate the media, and if you have a screw-on type container, then the media has to be loose or flexible enough to let you screw the lid on without pulling the hose off. (f.e. sand was too stiff).
2. Use a baffle between the input and output sections, so that water will have to flow down the container and back up.
The baffle could be made of any type of plastic, and secured with epoxy or hot melt glue - but it seemed easier to me to just use an extra piece of hosing.
Step 6: Connect the Hose to the Pump
I brought my pump with me to the dollar store so I could check which size of hose would fit it. In my case, 15mm hose worked perfectly just by pushing the hose over the outside of the outlet of the pump. A smaller size might work on the inside instead. A size that's slightly too large might also work if you secure it with a zip-tie connector.
Once you connect the hose, you can plug in the pump and submerge it into the water to make sure it works and that water isn't leaking anywhere it shouldn't be.
At this point, one end of the hose should be connected to the output of the pump, and the other and should have the female connector attached.
Step 7: Test Drive
Put the lid on the container and close it tight. Next, connect both hoses, and run the output hose up to your aquarium. While the final placement shouldn't matter, place the filter below the aquarium to begin in order to help the pump out a bit.
I also recommend putting the filter in a bucket just in case it leaks!
Turn on the pump. Water should flow down and fill up the container, and then back up and into your aquarium!
Step 8: Load Filter Media and Production Use
After shutting off the pump, lift the container above the water level, and then remove the connectors. Dump out some of the water and put in your media.
Be careful of the extension hose inside the container. It should go through the media to the bottom.
I used only a small amount of zeolite media for testing. Then lower the container and start the pump again.
Your fish may be curious and come to investigate the new item in the aquarium!
Step 9: Conclusion & Tips
This project works surprisingly well considering the low cost and the fast that it requires very little time or expertise. Also, the look of the finished project isn't terrible. That said, there are some points that could be improved:
1. Garden hose is really too stiff and a bit overkill for this use. It's far too easy to be adjusting the pump and have the hose come out of your tank and start spraying water everywhere! It would might be better to buy replacement filter hoses from an aquarium shop if you can find them cheap and they are the right size. Alternatively, regular clear aquarium tubing of a larger size would probably work just fine. (Actually a thinner tubing would work better - garden hose is thick enough that water can easily flow in just half of it, which makes it not so good for syphoning unless you have a very high flow). There are, however, two counter-measures you can take while still using the dollar store garden hose: First, use a suction cup to anchor the output hose inside your tank to make sure it doesn't mode accidentally. Second, cut the hose short so that it is just the right length as needed.
2. I recommend that if your container is large enough, make one hole in the center and one off-center. This way the internal extension hose can be attached to the one in the center and it won't have to move very much when shutting the container.
This is my second build. The first one didn't work out well. The first time I tried to glue the hose directly into the container using hot melt glue. Trust me, you want the quick connect connectors, and you want to use epoxy. Hot melt glue doesn't work especially well with flexible things and it leaked everywhere.
Don't undo either of the quick-connect connectors if the filter is below the water level even if the pump is off! (unless you have the filter in a bucket, of course). Water will of course come spraying out due to the influence of gravity.
The pump doesn't necessarily have to be in the aquarium just because it originally was. You can attach tubing to the input side of the pump so that there is less gadgetry in your tank - just be aware that you may have to manually prime the pump.
Obviously you could use a larger container - but you could also make more containers and connect them in series to make an effectively larger pump without letting the old containers go to waste when you upgrade.