Aren't sweepers more stringy and clear and from reading in the goniporas case they are more dense then normal heads/polyps? While goniopora do have sweepers, this to me looks just long a elongated polyp/head. Could it just be catching more flow/ the perfect amount of flow? My entire colony is the size of a softball and always looks like your longer tentacle and I doubt most are all sweepers since only the newer bottom heads are smaller on mine since are new/growing out. My tang brushes it always and so do my wrasse and no issues ever.
Study
The massive coral Goniopora tenuidens can develop elongated "sweeper" polyps. These are thought to be involved in aggressive interactions with neighbo...
www.jstor.org
"The massive coral Goniopora tenuidens can develop elongated "sweeper" polyps. These are thought to be involved in aggressive interactions with neighbouring benthic organisms, like the sweeper tentacles of other corals. The cnidoms of sweeper polyps and ordinary polyps of G. tenuidens from the Great Barrier Reef were compared. Sweeper polyps had significantly greater densities of elongate holotrichous isorhizas (34577 ± 3839/mg; mean ± SD, n = 6) than ordinary polyps (936 ± 371/mg; p < 0.05), while ordinary polyps had significantly greater densities of spirocysts (75994 ± 15992/mg) than sweeper polyps (19469 ± 7808/mg; p < 0.05). This suggests that sweeper polyps of G. tenuidens, like the sweeper tentacles of other corals, are modified for aggression, and that they probably act through nematocyst discharge. However, the scattered distribution of sweeper polyps observed on colonies of G. tenuidens in the field suggests that sweeper polyps may have other functions. "
