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Filtration
Types of filtration:
Contents
BIOLOGICAL AND HOW IT WORKS: In detail (The under-gravel filter).
MECHANICAL: Short! A homemade system described.
CHEMICAL: To be up-dated soon
NO FILTERATION: Is it so simple?
DIY UNDER GRAVEL FROM PIPES: Simple and works well!
There are many types of bio-filters, for example the under-gravel, wet/dry, trickle etc. Let us take the under-gravel filter for example:
Water is constantly sucked from under the bed of gravel on the tank bottom and recirculated out into the tank using an airlift or a power head. Some sort of mechanical filtration does take place as the gravel traps particles but what is more important is the biological aspect. A freshly set-up tank has what is commonly known as the New Tank Syndrome. Why? Because when a tank with brand new U.G. plates/pipes, sand, power head and fresh water is set up, it contains all kinds of bacteria, the good, the bad and the ugly. Now we start to add fish. Toxin ammonia starts to build up as a result of left over food, excretions of the fish, bacteria and invertebrates. It will build up to dangerous levels and soon fish will start to die! Except maybe the toughest. Of all the bacteria present in this situation is one type called nitrifiers but they are not present in sufficient nos. to help. First lets see what they do.
Nitrifiers consist of two types, the first Nitrosomonas, they use ammonia as an energy source and convert it to a less toxic nitrite. This nitrite is in turn converted into nitrate by the second type called Nirtobacter. Nitrate in turn is even less toxic but it too builds up slowly and can cause problems. Nitrate is highly soluble in water and can not be removed by the small water changes we make or by simple chemical means. So how do we get rid of nitrate?
Nitrogen is required by all life forms to live but we do not feed our fish nitrogen supplements, they get more than enough from the food we give them, the excess being given out as ammonia. Thus starts the cycle again and we end up with continuously more and more nitrates, which as mentioned earlier is difficult to remove!
Nitrates could be converted to nitrogen gas, which would escape into the air but its complex, and I will keep it for a later up-date. Sorry!
So how do we manage? We can simply plant plants in the aquariums; they too need nitrogen as a food source! The most convenient form of nitrogen available to them are the end product of the bacteria breakdown, namely nitrate. This they use to grow (convert it to green matter) and then we can trim the plants, plant the trimmings in our other tanks or gift them to our aquarist friends, thus nitrate is removed from our aquarium. Such a simple solution and it adds beauty too! For marine tanks algae scrubbers are used, as they are plants also (algae).
Now back to the U.G. Filter, the nitrifying bacteria need a large surface area to colonize so they are in sufficient nos. to covert all the ammonia generated, and oxygen to survive. Both these criteria are satisfied in the U.G. Filter. The gravel/sand granules have more than enough surface area for them to colonize in the quantity required and the slow water movement passing through the gravel brings ammonia/nitrite and oxygen rich water into contact with them, enabling them to do their thing! Due to these requirements the flow has to be continuous and long stoppages of water flow will kill these bacteria. This is the main reason to worry during power outages.
There are ways to avoid/reduce the effects of the New Tank Syndrome. Commercially available Nitrosomonas and Nirtobacter can be added in numbers to start converting the ammonia immediately. Sorry these are not available in India, but we can help ourselves by squeezing a sponge/floss from a power filter that is running in a long established tank. This will not necessarily provide the quantity of bacteria required but will definitely seed the new tank and hopefully they will multiply as you introduce more and more fish.
DRAWBACKS AND TIPS : NEW! NEW! NEW! Feb. 21st. 2000
Mechanical:
This is exactly as the name suggests a mechanical media is used as a filter element. This can be a sponge, floss, and filter canvas or a mesh of required size. A powerhead or pump is used to flow water through the filter element. Generally a pre-filter is used to avoid choking the main filter with debris as it has pores in micron sizes. The pre-filter can be regularly cleaned without disturbing the main filter. These types of filtration give very clear water out put but do not mistake water clarity for quality. A biological filter used along with it gives good result.
After some use it too collects nitrifying bacteria and becomes partially a biological filter also, but it can not keep up, as its surface area is too small to hold the quantity of bacteria required for biological filtration.
A simple but effective system has been assembled with parts freely available in India. The pump used was a Tullu 1/8 HP, with a brushless motor to keep the noise factor down. In line an Aqua Guard filter casing with their element was used. The filter element porosity was 4 microns as told to me by a representative of the company. The total cost being Rs.3000 aprox. The result was very good with excellent water clarity for a 4 ft. x 1.5ft. X 1.5-ft. tank. Only drawback is that the pump gets hot when used continuously, it would work out really well if a means to cool it can be added. I really did not work on the cooling aspect except mentally as by then I had bought an Ehime external filter.
Reverse osmosis is also a type of mechanical filtration, it is still very expensive and there is nobody yet manufacturing it for aquarium purposes in India.
Chemical/biological filter units can be added in line to enhance water quality.
Chemical:
This type of filtration needs a better understanding to be used safely. Best left to the advanced aquarist. Activated carbon cleans the water by a process called adsorption. It will keep on absorbing till it reaches saturation then suddenly it will release all it has taken in! So suddenly it overloads the water with all the toxins it took out and there is no way to know when this to happen. Use it to serve your purpose and then discard it, though there is a way to reactivate it, it's just not worth the trouble. Carbon should generally be used to take out the medications added to the tank after the period of treatment.
Ozone too is used but it must be monitored to ensure the safety of the fish. A precise dosing is required, as it is fatal to all inhabitants in excess.
No Filtration:
This is used by most breeders and stockiest of fish. Only an air stone is used but the water changes made are regular and large, discus breeders sometimes change upto 90% twice a day! This is usually in bare tanks, so vacuuming up any debris and left over food is no problem. If conditioned/heated water is to be used, a large storage tank to pre-condition/heat the water is required. Otherwise a de-chlorinator like hypo can be used to take the chlorine out, in the case of chlorinated municipal water. It's a lot of regular and time-consuming work, so it's not as easy as it sounds!
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DIY Under-gravel filter from pipes:
The U.G. is nothing but a grid of plastic pipes with holes on the bottom and an up-lift tube on the top. You will need to be handy with your hands AND:
1) Plastic pipe: 3/4 inch Aprox. Length = 4x length of your tank + 2x breath of your tank.
2) Plastic pipe: 3/4 inch Length = Height you want the Powerhead to be at and a 3/4 to 1 inch reducer socket: 1 no.
3) Plastic elbows: 3/4 inch, 4 nos.
4) Plastic Tee's: 3/4 inch, 5 nos.
5) Drill with 1/16-inch drill bit. (Optional)
6) Hacksaw to cut pipe.
7) Solvent glue for plastic pipe.
Step 1: First make a frame as shown under, dry fit it (do not use solvent yet). Fit it into the tank and check if it needs any changes made to its dimensions. Make them if needed.
Step2: Then number the pieces and disassemble, if you think it will be easier to make the holes unassembled OR join it by using the solvent glue making sure that the up-lift tee is properly placed (as shown in the top view dia.). Make/drill the holes in case a drill is not available use a 1/16-inch thick nail by heating it and using it while it is still hot to make the holes in the plastic tube. The holes should be aprox. 1/2 inch apart. Now you can assemble it using solvent glue. Remember the tee for the up-lift tube is on the other side to the holes drilled.
In case you want to use a bubble airlift, take a piece of 1 inch. Plastic pipe, put it into the reducer socket in place of the powerhead and an air stone into the pipe. As the bubbles rise they will draw up water from the up-lift pipe hence the under gravel grid. You may use this for only small size tanks, as their water flow capabilities are not high.
In case you require further clarification pl. contact me at: <rainbow@pn2.vsnl.net.in>
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Last Revised: 21st. Feb. 2000.