1. External filters canister type.
The illustration shows a conventional canister type filter. It consists of a canister (the main body of the filter) and a head (cover), which is removable, but is sealed to the canister. The water-cleaning material (filler) is placed in the canister. In the head – the pump.
Water from the aquarium through one of the tubes (usually wider) by gravity flows into the filter canister. (Water flows from top to bottom, so all canister filters should be placed below the water level of the aquarium.) In the canister, water must pass through the bed of filler and be cleaned. Then it is pumped out by a pump located in the head of the filter, through the second, usually thinner, tube back into the aquarium. So, in short, the canister filter works.
Small comments about the quality of the filters:
– For ease of maintenance, the simultaneous use of several types of filler, a uniform flow of water through the layers of filler filters should have trays (baskets). Filters without such trays are not universal – they can be used only as additional to the already existing filter.
– Filters must have faucets on the inlet and outlet tubes. Without them, filter maintenance turns into flour.
– Water enters the filter by gravity, and the filter pump is designed so that it pumps only water, not air. Therefore, if you simply lower the free ends of both filter tubes into the aquarium, water will not flow through them. It is necessary to make the water from the aquarium flow by gravity into the filter. Only after the canister is filled and the pump is in the water – the filter will work. Therefore, in order to run most modern canister filters one has to carry out a not very pleasant procedure – suck water from the inlet hose until it starts to flow by itself, and then attach this pipe with pouring water to the filter. (It is good that such a procedure should be performed quite rarely). Therefore, in order not to pour water on the floor and on the furniture, a pallet is necessary for the filter.
– It is possible to avoid difficulties with running the filter if the filter has a pump (manual) for sucking water from the aquarium into the inlet hose. If not, then you can put a pear with a valve on the inlet hose. (In the price list pear is in the accessories section).
The main parameters that determine the quality of the filter
– pump performance – recommended 2 – 4, and for saltwater aquariums up to 10 times the passage of aquarium water through the filter every hour;
– the volume of the canister affects the amount of biomaterial, and therefore the quality of water purification;
– the quality of performance takes into account the reliability of the filter, the convenience of its service, the ratio of price and quality (estimated on a 5-point scale). At the same time filters of one category are compared.
Some data on some canister filters: