Nems bleach (turn white) when they don't have enough light. Depending on where it sits in the tank 150w halide could be more than enough light for it. I have a green bta that only lets about 1/4 of its self be exposed to light, the rest of it hangs out on the under side of the rock. On the flip side my rose bta sits directly on top of a rock exposing all of its self to light. Both are under 150w 14k halides about 1/2 and 3/4 up the tank respectively. As long a your parameters are as they should be and stable, and they aren't moving around or turning white, they should be okay. Btas can lose their bubble tips for any given unknown reason, doesn't mean anything is wrong with it. My green lost its bubbles not to long after I bought it, but my rose still has its bubbles.