You might be able to throw an encrusting monti in one of the holes. They tend to not be overly agressive. You maybe to use kalk or something later to keep it from getting to close and encrusting over the Blastos though I guess.
I’ve had the opposite experience with Montipora and don’t add any encrusting montis to my main rocks anymore! Ended up being a nuisance and difficult to keep in check. But, maybe there are some specific varieties that would be a different experience?
Sorry, I guess I should clarify - by overly agressive I meant attacking/stinging. The concern would be the agressive growth that can often take over slower growing corals. After thinking about it a little more it would probably be a bad idea. Based on the reading I've done on Blastos recently and trying to keep mine from any coral warfare, Blastos are super weak when it comes to defense and attack. Montis are generally as well but they tend to grow so fast that they can overtake other corals. I don't know who would win in the battle between Blastos and Montis so I would keep the monti from encroaching by using kalk paste to knock it back a couple inches as it got close. Just a suggestion. Leptos or Pavonas would work as well.
