DIY: Biological/Chemical Filter For Aquarium

I have been toying with the idea of making my own biological cum chemical filter for a long time. I am using a overhead filter but it is kind of small to add in any other media after putting in the filtration wool.

Since my overhead filter is only fulfilling the mechanical aspect of the filtration system, this project will enhance the biological and chemical step.

There are three components to the filtration system:

- Mechanical
- Biological
- Chemical

MECHANICAL - This is the first step in the filtration of fish keeping. Physical debris such as fish waste, uneaten food and decaying plant matter will be sucked in by the filter/powerhead. The aquarium water will then return to the tank while the debris will be left behind on the filtration wool which can be easily removed for cleaning.

BIOLOGICAL - As ammonia and oxygenated water passes through the media (eg. ceramic rings, bio-balls, etc), a colony of beneficial bacteria starts multiplying itself on the surface area. These bacteria breaks down the ammonia into nitrite and nitrate then further into harmless nitrogen.

Ammonia in high concentrations is toxic to fish. Google "Nitrogen Cycle" to learn more.

CHEMICAL - Activated-Carbon removes many harmful elements from your aquarium such as copper, chlorine, dissolved proteins, and carbohydrates. It also helps to absorb odors and make the water clear.

After watching a few videos on youtube, I thought that the DIY is quite doable but all the tutorials require a certain media called K1 (the surface area allows the good bacteria to multiply on them).

I do not know whether it is available here in Singapore since the tutorials are all overseas-based. I decided to pay Qianhu fish farm a visit but all they had were ceramic rings and activated-carbon. They have bio-balls too but those would not fit into the mouth of the water bottle (which is required in this project).

I have seen some tutorials using straws cut into shorter length instead. I wonder is it okay to use straws in place of K1?

Anyway, to start building your own biological/chemical filter, here are the things you will need:

- A mineral water bottle
- Soldering Iron (to make the holes)
- Airline Tubing
- Cable ties
- K1/Ceramic Rings (or any other media you can find that can fit into the mouth of the bottle)

A mineral water bottle

I used the soldering iron to make four holes on the cap

Make another hole on the neck for the airline to go in.
Make sure the hole is slightly smaller than the airline so it will not slip out easily.

Make another few holes at the bottom of the mineral water bottle

Insert the airline a few cm into the hole on the neck

Secure the remaining airline and suction caps to the bottle with cable ties

Since I cannot find K1 or its substitute yet, I bought activated carbon
and turn this project into a chemical filter instead.

I removed the activated carbon from their mesh bag and screwed the mesh
bag under the cap to prevent the activated carbon from falling out through
the holes in the cap when the mineral water bottle is inverted in the tank

This is how the completed bottle looked like.
The bottle will be turned upside down and suctioned to the side of the tank.

As the airline starts bubbling, water will be suck in through the holes in the cap.
The oxygenated water will rise through the activated carbon and exit through the holes on top 

Watch my DIY Chemical Filter in action below.

Alternatively, open this video on youtube.


I have since re-modified my DIY Chemical Filter by adding cut-up straws into the bottle which now functions as a Biological Filter as well.

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