If you had 6 to 8 fronts in a 4 foot (55 or 75 gallon) they could be comfortable in there for about 6-8 months if you get them at about 1.5 inches long. During that time you will likely have one or two that will grow faster than tankmates and be very dominant and aggressive, that will be the alpha and beta males (not 100 percent but most commonly found). After that time you will need to house them in 6 foot tank or larger, especially the more you have . I had 6 burundi fronts growing out in a 6 foot 125 and the alpha was tearing them up , moved them to a 7 foot tank and its much better now. (I still have one or two that have fin damage from that time, likely will have it forever) Fronts are aggressive to each other but wimps with other species of fish so keep them species only unless you can watch them closely and make changes when needed.