I have heard that there are a few different types of carpet and all have different tendencies and needs. I have heard that S. hadoni is the most common and easier to care for. It is a sand dweller but will usually foot itself at the base of the rockwork. It usually maxes out at 24-28". I have heard that they can be fish eaters.
I have heard that S.gigantea is one of the most difficult to care for, and/or most difficult to find a "good one". They will usually attach at the base of teh reef, but usually more on the rockrock. They are not fish eaters IME. Requires strong lighting (much more so than the hadoni), and some folk say that they require (or at least do better with) surge tanks. Despite the name, the gigantea is the smaller of the 3 hosting "carpets at about 22" max.
I have heard that the S. Mertensi is rarely imported. Probably due to its size.. They usually go about 36".. usually perched high on the rockwork.. Strong lighting needed.
S. helinthus (atlantic carpet) I have heard is a proven fish eater.. Perches on the rock dont get nearly as large... Non-hosting species that has even consumed many clowns. Not one That I would recommend for ANY tank
S. tapetum.. Very colorful small non hosting carpet anemones...
H. Magnifica, like the S. gigantea are supposed to be very difficult to keep happy. They will require very strong light and very strong flow. Unfortunately they are the "natural" hosts for ocellaris clowns.
FWIW, I used to keep a Rose BTA just a few inches under a 400w 10KK being overdriven by HQI ballast. The greens tend to shy away from lighting that is too intense, but the roses will acclimate themselves if given the chance. My recommendation would be to try another BTA.
