My skimmer is a venturi model run with ozone. It requires two pumps to operate, one supplies water and one circulates water through the venturi.
I only used 6" of acrylic because that's the piece I had laying around. I can see the bubbles fine in that and it keeps the rest of the unit dark so algae doesn't grow inside.
The top reaction tube is easily removable to clean. It has a plastic compression fitting from a sink drain. I give it a half a turn and the top comes off. There is also a tube to the collection cup that drains into a five gallon bucket. When I remove the reaction tube to clean I squirt some bleach into the cup to keep it clean and the tube from growing algae.
It is important to have the water enter on an angle so it swirls around and doesn't just crash into the other side of the skimmer.
The effluent goes into the bucket that has a DIY overflow switch on it. It overflowed once when 24 urchins spawned at the same time.
The overflow switch is easy. I took two wires from the GFCI protected receptacle that runs the pumps of the skimmer and put them into a plastic container that has holes in it hanging near the top of the bucket. If the water level in the bucket hits that plastic container, the GFCI trips off stopping the skimmer and preventing water from going on the floor and my wife going nuts.
I use that same switch all over my house to shut off things if there is a leak.
The skimmer is probably 20 years old and I never had a problem with it. It does have a small air pump on it because it is so tall the venturi is not capable of providing enough suction to draw air so far down.
To adjust the water level in the skimmer I built a valve on the outflow. The valve is not capable of shutting off the water completely but it can make fine adjustments. It is basically an elbow with a big, flat head nylon screw threaded into it. (it is actually a screw that holds the seat on a toilet bowl) To adjust the valve, I turn the end of the screw that is sticking out of the elbow. That moves the large flat head of the screw towards or away from the output opening of the elbow. (The screw head is about 3/4" wide)
The large adjustment on the skimmer is a regular PVC valve on the input but that doesn't give me the fine adjustment I need.
I also have a 3/8" clear acrylic tube on the outside of the skimmer that is the sight glass and allows me to see the exact water level in the skimmer because due to it being PVC I can't see the top of the water level in the unit.
I adjust it so the water level is just near the bottom of the reaction tube.
The bottom of the skimmer has a gate valve that I use to remove water from the tank.
