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FAQ - Filtration

How to handle an external filter input and output? I didn't find it in the plan.
Water intake in the tank overflow pipe is visible in the background DIY section (Pic. 4 and Pic. 5) and in the overflow plan. The return pipe is presented below. It is on the opposite side of the overflow pipe. The flexible hose goes over the aquarium upper edge, through the canopy cut-out and ends at the water level on the right side of the tank.

OPic. 1 - Return hose end Pic. 2 - Return hose end Pic. 3 - Return hose end Pic. 4 - Return hose end

How big should be an external biofilter for 420 L aquarium?
An important thing is the filter media volume and it should be around 5 - 10% of an aquarium volume. It means approximately 20-40 L of filter media for 400 L aquarium. The total filter volume of 50-60 L should be enough.

How often to change filtration media in an external biofilter?
Basically, filter media should never be changed. Destroying the filter foam takes years. Only the filter floss can be replaced more often (attention, don't use the cotton wool but the special synthetic filter floss for aquarium purposes!). The floss will serve a long time but as it is often placed in the 1st filter chamber, it is dirt first and it is harder to clean. I use to replace it with a new one once a year, two. The foam is washed if needed, when it is clogged. It shouldn't be done frequently because the rough dirt shouldn't get into the filter. The filter foams are never cleaned all at the same time. It is fine to wash foam carefully from one filter chamber in aquarium water and the next one can be washed by next two weeks etc.

How to cycle an external biofilter in order the essential bacteria could reproduce?

Bacteria are everzwhere, so they will be also in the tank and will get into the filter soon. However, they need some food (ammonia and nitrites rising from the fish food and other organic matter like fish feces etc.), so that it is a good idea to cycle the tank using some modest fishes (i.e. livebearers) and feed them sparingly to allow the bacteria to reproduce. The best idea is to use the water from another cycled aquarium or twist the foam from cycled filter to the main tank carefully.

May I put the heater into the last filter chamber?
Sure, I use to use it in the same way. It is the best placement of the heater if it is placed outside the tank because the heated water flows directly into the aquarium without the major heat lost. If the heater is placed in the 1st chamber, the heat lost during the water flow through all the filter chambers will be higher.

May I use the common yellow foam as a filtration medium?
A foam used in older mattress isn't suitable for filter purpose as it is too dense and undergoes to the disintegration after some time. The polyurethane foams are useful (blue or black foams known as Filtren).

How to solve an internal biofilter for 550 L aquarium? What should be the dimensions, media, pump?
See the picture below. The filter floss layer thickness is optional to allow the foam (also known as Filtren) placed under it to be removed easily. Also the foam under the floss isn't needed. This chamber will be cleaned most frequently so the floss and foam (if it will be there at all) will be washed. I recommend the 2nd and 3rd chamber width under 8 cm. The wider chamber is unprofitable because the internal volume of the filter foam will not be used by bacteria. They need oxygen reach water and in the middle of the foam the water contains low concentration of oxygen. Ceramic rings in the 4th chamber are also optional but it is a good idea to place porous material like these rings as they don't get clogged and don't slow down the water flow. The last chamber can be filled with the ceramic rings only. Another thing is placing the heater into the filter. It doesn't take place in the main tank and aquarium without the technics in like heater etc. is more aesthetic. The heater can be placed in the 4th chamber but only with the ceramic rings because it could damage the foam while heating. This is only the raw layout of one option. It can be modified anyhow. The basic thing is to provide the water flow through the whole chamber so the dividers have to be made in zigzag pattern. It is hard to design the accurate thickness and density of the foams in relation to the pump output. It has to be adjusted bz testing. Maybe the scheme provided here will work accurately but maybe the Filtren TM 30 will be too dense and the water flow will be slowing. Then the return pump will drain all water from the last chamber and there will be not adequate water supply from aquarium. I recommend to make the bigger cut-out on the 1st chamber which can be controlled using the plexiglass with teeth. It prevents the fish and plants to get into the filter. It has to be designed in order the plexiglass could be moved up and down to adjust the water flow into the filter. The plexiglass can be without the teeth, sure.

Why are the chambers in the filter scaled from the highest to the lowest? Depends it on the return water drawing speed or the water level decreases with the decreasing permeability of the firmly clogged filter?
The chambers are scaled to allow the water to flow easily through the whole volume of every chamber. The interdividers also helps. Water flows from the higher chamber to the lower. Also some filter reserve is provided to prevent the filter spill. Definitely, it is possible to build the filter containing the chambers of an equal hight but I think that the water flow has a better dynamics with scaled chambers.

Copyright © 2003 - 2012 Robert Toman



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