Yes, exactly. In fact, it is becoming popular (with some in the know) to perform a formalin bath at least once in-between TTM to prophylactically address the possibility of velvet & brook. I'm not so sure I like it, as formalin is a known carcinogen. But it seems to be working well (at least in the short term.) I prefer to reserve formalin for emergency use only; especially since I have found acriflavine to be a suitable nontoxic alternative.