I have heard that keeping anenomes under fluorescent light was not possible ....this now seems to be incorrect.
First of all congratulations on your success with you BTAs!
I have heard that too. It is just another example of people thinking they are experts because they can parrot something they read in a book or article, without have much experience themselves.
While clownfish host anemones do have minimum lighting requirements (which in my opinion cannot be made up for by increased feeding) the requirements for some species are not as high as I see posted on some reef forums.
For 10 years I (and many others) kept anemones under normal output fluorescents in tanks less that 18" deep. We did pack as many bulbs over the tank as we could fit, usually 4-5 bulbs equal to the length of the tank. It usually worked out to about 3-4 watts of NO fluorescent light per gallon. I usually fed at least once a week, sometimes twice. Once I figured out how to pick out a healthy anemone, I was able to keep them until they out grew my tank or there was some sort of tank catastophe.
Under these conditions, I was able to keep BTAs, haddoni carpets(saddle carpets) and sebae anemones (H. crispa). I have had many BTAs and saddle carpets for 7+ years and have a sebae that is over 12.
IME, the three other main clownfish hosts, LTAs (M. doorensis), ritteris (H. magnifica) and giant carpets (S. gigantea) needed more light than I could provide.
With the advent of PC lighting there is no reason to ever go below 4 watts per gallon over a tank of 18" or less. I currently keep 11 different host anemones of 6 different species in 6 different tanks(some tanks contain more than one species). Until very recently all have been under PC bulbs and all but 2 range in age from 2-12 years.
I've been doing a couple trials with a ritteri and a giant carpet in the last few months.
The ritteri is being kept ~8"(air +water distance) under a 65 watt 6500k landscape fixture. I have had him for ~2 months and I'm feeding him about 5 times a week. So far he has not shown any signs of distress and seems to have grown ever so slightly.
The gigantea is a different story. He was about 11 total inches below 2-65 watt PC bulbs and was also being fed 5 times a week. For the first couple months he looked pretty good. Over the course of the next two months he started to loose his blue tips, his tentacles grew shorter, and his size decreased. At the same time, he showed no signs of what we normally consider to be an anemone in distress. In fact, had I not seen him before, I would have thought he was a very healthy anemone. Two week ago I put a 150 watt DE Metal halide 13 total inches over this shrinking carpet. Within hours he was already looking better. Now, almost two weeks later, he has increase his size by one half, his tentacles are noticably longer and the blue tips on his tentacles are starting to come back.
It is too early to tell about the ritteri, but as for the gigantea, IMO they are one of the few species that absolutely need metal halide lighting, even in a shallow tank and no amount of feeding can make up for it.
I wish you continued luck with your BTAs.