I'm not sure what sort of borers you have, but there is an very old fashioned way of dealing with plant and tree stem borers, albeit tedious. It might be worth a try before ripping your tank up to boil the conks. Insert a thin, flexible wire into the borer holes and stab the little buggers to death with it. Just keep at it on a daily basis every time you notice a new bunch of sawdust.
What animals do you have in this tank? You could also try tamping in some cotton ball pellets soaked in some non-denatured ethanol such as Everclear or even straight vodka, or go after them with flexible cotton swabs saturated in this if the holes are large enough for these to fit into and jab around. If it this doesn't work, you can spike some party punch with the left-over "chemicals" or make a martini. Isopropyl (rubbing alcohol) would work too, but it is denatured so alcoholic bums can't evade the liquor tax without dying, and I really don't know if it would leave any possible toxic residues to eventually harm your animal inhabitants. I doubt it, but this is arguable, so it's better to be safe and use the stuff you have to pay taxes on.
It's lots of work, but probably more fun than taking your tank apart and boiling stuff.
-----
Patty
Lost River, Idaho
D. auratus blue
D. galactonotus
D. imitator
D. leukomelas
D. pumilio Bastimentos (soon)