i have the 14k phoenix in my 40B i can keep acro on the sand bed. i have a lumenarc 3 reflector and 2 vho's i have some that are one inch under the water line and some on the bottom. the ones on bottom do just as good. acro bali slimer, birdnest, hydno on top, staghorn & mili on bottom all are averging about 1/8" growth every week or so