If you are looking to do this on a grander scale then I would recommend 6 to 10 eels as an ideal setup for a home aquarium. If this is your goal then you will want to plan for 1 square foot of open sandy substrate per garden eel pair. Be sure to factor in any areas of the tank's bottom surface which you plan to cover with corals or rocks as these will have to be subtracted from the available eel space. The space allocated to the eels will need to be contiguous so that they can mimic their colonial housing inclinations. The bottom line is that any aquarium housing Spotted Garden Eels will need a large open sandy area and this will likely be inconsistent with our usual inclinations to fill most of the aquarium's space with rocks and corals with very little real state devoted to the open sand areas. The ideal tank will have a height equal to or greater than 24 inches and a depth (front to back) of at least 24 inches. A standard 120 gallon or 180 gallon glass aquarium is in my opinion ideal for a garden eel setup. These tanks will give you the needed room to incorporate some live rock and corals into the display making for a more aesthetically pleasing setup. Cube tanks with at least 4 square feet of surface area (24 in x 24 in) and 24 inches of height are also a good place to start if you are looking to go with a cube-shaped tank. Keep in mind that the bigger the tank the more space you can devote to live rock and corals.