Aquarium air valves and fittings come in different styles. A straight fitting connects two tubes; elbows allow tubing to go around corners without kinking; an aquarium "T" valve splits a single line into two; a cross fitting splits one line into three. Keep in mind that you need a powerful air pump to split the airline. An aquarium air check valve like the offering from Hagen prevents water from coming out through the tubing. An aquarium air control valve, or gate valve, lets you adjust the air flow.
Valves and Fittings
Filters
$2.89
Two Little Fishies
Two Little Fishies Micro Valve Barb x Barb - (6 per pack)$10.20
Two Little Fishies
Two Little Fishies 12 Piece Aquatic Micro Airline Hose Fittings$5.72
Tom Aquatics
Tom Aquatics Airline Straight Connector - 4 Pack$1.99
Tom Aquatics
Tom Aquatic Airline Elbow Connector - 4 Pack$1.99
Vivid Creative Aquatics
Multi-Tube Clips (Black) - Vivid Creative Aquatics$4.95
Two Little Fishies
Two Little Fishies Micro Valve Barb x Thread - (6 Per Pack)$10.20