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7.2.3 FLOW METERS:

Devices that are piped in line to determine what the exact amount of water that flows through your pipes, and through your tank, is.

Not a necessary part of your system, but handy, especially if you want a high degree of control over what is going on in your tank. The price of the flow meter is determined by the degree of accuracy that you are looking to get. Calibrated flow meters are the best, but cost quite a bit. Check with scientific supply houses if you are interested. Prices vary from around $50.00 for the least accurate ones, to about $250.00 for the real good ones.

7.2.4 NEEDLE VALVE - ANGLE VALVES:

Unlike ball valves, shut-off valves, and true union ball valves, these types of valves allow for very small adjustments in the flow rate.

Very good to have, for instance, to adjust the flow rate going into your columnar protein skimmer. Needle valves are usually only available in real small sizes. Angle valves which also allow precise control over the flow, can be bought in much larger sizes as well. Plan on spending between $20.00 and $30.00 depending on the size, and the quality that you are looking for.

7.2.5 FOOT VALVE:

Similar to a check valve. In fact foot valves contain a check system, but are, in addition, equipped with a screen to prevent large particulate matter from getting through. They are not a substitute for a fine filter, because they only prevent larger types of material from getting into your pipes and tank. The real fine particulate matter needs to be removed with a proper fine filter.

Can only be used in submersed form. Not in-line. Although some hobbyists use them, they do not have a wide application around reef tanks.

7.2.6 GATE VALVES:

A form of shut-off valve. Same principle, but far less precise adjustment. For just opening and closing off a water line they are all right to use.

Often used in very large aquaria, but not so often in home reef systems.

7.2.7 SOLENOID VALVES:

Solenoid valves are electrically controlled valves. They serve only an on or off function. Nothing in between, they do not allow for a flow adjustment. Such is not their purpose.

Two types are commonly available: normally closed (NC) and normally open (NO). When energized, meaning when an electric current is sent to them, the valves change internal position. The NO valves close, and the NC valves open.

Solenoids are used for many applications. For example, they are used in conjunction with pH controllers to dispense carbon dioxide. When a NC solenoid is energized, it opens and lets CO2 through. When the pH has changed, and the controller shuts off the power to the solenoid, it closes and stops carbon dioxide from getting through.

They can also be used with columnar protein simmers to prevent the skimmers from emptying itself when the power goes off, or when the pump fails (this is appealing to many hobbyists who have filters with small sumps that cannot hold the excess water coming out of the skimmer, during such a power failure).

Many other applications for solenoids exist, too many to mention here. Some of them are discussed in _Advanced Reef Keeping Made Simple (I)_, for instance their use in conjunction with a gravity fed water refill system and a float switch.

7.2.8 ACTUATED VALVES:

Electrically actuated valves do not have much of a use in home reef tanks, but are sometimes used, in line, to create an alternating water current between two different water inlets into the tank.

For more details you may wish to refer to _Advanced Reef Keeping Made Simple (I)_ as well.

7.3 CONCLUSION:

Although you may not have used many fittings and valves in previous aquariums that you have kept, around reef tanks, especially the more sophisticated types, you will find that they are either a requirement, or that they will increase safety, or that they will make your life a lot easier.

If your are setting up such a tank, refer to my two other books for more details on many other applications not mentioned in this one.

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