DIY Bulkhead Aquariums

Plan the overflows. Using a dry-erase marker, draw out the location of the overflows and the bulkheads. Purchase the bulkheads ahead of time and use them to trace the circle where they will fit.

Drill the glass where the overflows will go. Do not try to drill tempered glass; it will shatter. If the bottom of the aquarium is tempered glass, which it likely is, you will need to attach the bulkheads to the back or side panels and drill the holes through them. If you are going to drill through the side, remember to include space in the overflow for a right-angle elbow bend pointing up. Drill slowly and carefully using a special glass grinder.

Attach the bulkheads. Bulkheads come in two pieces with a rubber washer between them. The washer should go on the side of the bulkhead that will be in the water. Insert the bulkhead into the hole and screw the larger side over it. Tighten them as much as you can with your hands. They are plastic and the threads will strip easily if you use a wrench. Leave them in place while you build the overflows to ensure proper fit.

Build the overflows. You can build them out of glass or acrylic, although acrylic will be easier to cut at home than glass. The overflows are tall rectangular boxes with one side on the back or side of the aquarium. You need to attach the other three sides inside the aquarium. The top of the overflows should sit about an inch below the top of the tank to allow water to flow into them and not out of the aquarium. Some places sell black covers for the overflows, and you can use these to design the overflows. The bulkheads will be inside the overflow so that water flows over the top and into the overflow box, then out through the bulkhead.

Glue the overflows in place. You can use glue to adhere the glass or acrylic to the aquarium, but you must coat all seams with aquarium safe silicone sealant. The glue will be toxic to the fish so you need to encase it in the sealant to prevent the toxins from leaking into the aquarium water. Also, the sealant will create a watertight seal around the overflow.

Build the plumbing inside the overflow for the outlet bulkhead. If you leave the outlet bulkhead as is, water will flow over the overflow and crash to the bottom, creating a loud waterfall-like sound. This is usually not desirable. To counter this, you need to raise the inlet of the bulkhead up using PVC. Cut a section of PVC pipe that is about a half inch to an inch shorter than the top of the bulkhead. Fix this into the bulkhead. Then build a hook over the top, so it looks like an upside down J. This will prevent the water from flushing down the pipe.

Plumb the bulkheads with PVC pipe into the filtration system so that the water will flow from the overflows into your filter or sump.

Turn on the aquarium water pump to test the system. Keep a close eye on this system while it runs so you can make adjustments as necessary. First, you want to make sure it doesn't flood the floor. Second, you may have to make adjustments to reduce noise from the water. If the upside down J-shaped pipe in the overflow makes a sucking sound, drill a small hole in the top of the J at the bend to let in air. If the sound of the water flowing over the overflow is too loud, raise the height of the upside down J pipe to let the inside of the overflow higher fill higher with water.

Simulate a power outage by cutting all power to the system. The flow of water should simply stop. Water should no longer pour over the overflows or leak into the overflows.

Turn the power back on all at once. The system should start up without flaws or flooding.