When you hear the term "bower builder," maybe your first thought is a bird - the bowerbird. You may then ask, what is a bower? Simply put, it's a dwelling, often elaborate and leafy in construction. So what's this have to do with cichlids?
If you keep African cichlids, especially from Lake Malawi, and you have a sand or mini-gravel substrate, you may end up with a bower in your tank. Within the context of fish, a bower is a typically well-defined depression, often on a raised mound. Cichlids aren't the only Perciformes to exhibit bower building, which is primarily a social behavior exhibited by males for mate attraction. Bass, perch, and bluegill are other common freshwater fish that perform this ritual.
If you're interested in the nuts and bolts of bower building by Lake Malawi cichlids, check out this outstanding scholarly article from the journal Frontiers in Ecology an Evolution. Yes, it's a research article, but it's readability is rather high for the lay public, in my opinion.
The Cichlid Room Companion
Tropical Fish Hobbyist
American Cichlid Assoc.
African Cichlid Hub