These skimmers usually require three pieces of equipment typically not sold with them: an air pump, air stones and a water pump. Total skimmer cost depends upon the kinds of equipment needed to run the skimmer properly.
The water pump injects the water to be skimmed into the unit. Some people use gravity to feed surface overflow water to the skimmer or divert part of the main circulation pump's return flow into the skimmer to eliminate the need for a dedicated pump. Otherwise a powerhead in the sump usually suffices for the water pump. Some arrangement should be made to gather surface water for all forms of skimmers.
The air pump must be large enough and a sufficient number of air stones must be driven to make the skimming column milky white. In some smaller skimmers one medium sized air pump like a Tetra Luft G and one air stone will be sufficient. Other skimmers need a lot more to perform optimally.
Speaking of air-pumps, we find it baffling that folks who would consider spending $250 for a water pump to drive a different style skimmer totally reject spending anything on that order for an air-pump.
Air driven skimmers should use limewood air stones which will need to be replaced from time to time. Cheap limewood air stones have a reputation of needing to be replaced much more often than high quality stones. Coralife limewood air stones have a good reputation. Air stone replacement rate depends on your tank and skimmer; some people need to change them every 2 weeks others only after 3-4 months. It is believed that having a high air-flow prolongs the life of airstones
Some hold that any skimmer under 4' high and 4" in diameter is too small for anything over about a 20 gallon reef.
2. Venturi Protein Skimmers (我用緊呢個)
These skimmers use the Bernoulli effect of the venturi valve to inject air bubbles into the water. This obviates the need of an air pump and air stones. The penalty is that a relatively large, high pressure (read expensive and power hungry) dedicated water pump is mandatory for the venturi unit to inject sufficient amounts of air.
A particular commercial venturi skimmer may or may not come with a water pump. If it does supply a pump, it may or may not be sufficiently large to run the skimmer properly. At least some of the venturi skimmers easily available are not very well designed.
Venturi valves require occasional cleaning of the air opening. This is as simple as reaming the opening out with a pipe cleaner every few days. An acid bath may be required if the unit clogs or gets coated with mineral deposits.
Most venturi style skimmers are more compact than CC skimmers. Manufacturers state that they are more efficient, since they (supposedly) inject more air. Many suspect that design constraints (back pressure severely affects venturi performance) have more to do with the manufactured height (who would want a top injected 4' skimmer with air only in the top foot of water?). Properly designed venturi skimmers are tall to maximize air contact time, and require pumps that can handle backpressure.
3. Down-draft Skimmers
This style skimmer was first commercially introduced as the ETS skimmer. Currently there are several on the market. This skimmer using a high pressure stream of water injected downward into a column of bio- balls to suck air into the water stream and break the air up into tiny bubbles. They do this very well, with some casual testing indicating air movement on the order of 10 times the volume of equivalently pumped venturi models.
The cost of ETS skimmers is relatively high, but expected to drop as competitors enter the market. Cost of operation is high due to the need for a huge water pump. The use of Iwaki 55s and 70s on base unit ETS skimmers is common. This size skimmer is appropriate for a 70-135 gallon tank. e.g. The skimmer pump may be larger than many use for the main tank circulation.
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發表於 2011-9-19 10:37:46
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