One of my apothogen (sp) bulbs, the only one that grew, anyway, never really did well in either of my tanks. But now that it's in with Marina (Betta) it has started groeing like crazy! What could cause such a growth change?

Aponogetons are seasonal plants. They tend to grow like topsy then they have a dormant period. It could have been triggered to grow by the move to the new tank. Is the betta tank warmer than the other tanks? That could have been a trigger if it is.