Oh great! That's good ^_^ makes me explaining things a little easier and I don't have to write an entire essay either haha. Although I've gotten better at simplifying it down to just colonizing a group of BB lol
(No worries, I'm actually working at CBLS while I'm on here XD)
And you're right, doing a full or 100% water change can harm the BB in the tank. BB is extremely adhesive and you can't really rub it off but there are two things that can kill it: Tap water with chlorine in it (so whenever you want to swish out the cartridge, use old tank water or new water that's already been conditioned) and drying out. BB is not only in your filter but on the tank walls, the gravel and any surfaces that exist in your tank.
Do you have a gravel vacuum to use on the tank? Aqueon has a nice small 4 inch one that you can get that's great for small tanks! I can give you a link for one if you do need/want one. So basically you just don't want to clean the surfaces of your tank with tap water or let them dry out, not that you have lots of BB in there with just one fish, but it's still the fact of the matter.
If you can, and I know grad's are super busy often, at least switch to doing one if not TWO 50% changes in a week. So say one 50% Wednesday night and another 50% on Saturday. This makes it so that you don't have to do a 100%, but you're still cleaning the gravel/fish waste/and other organic compounds out while still replenishing the water. It will keep him healthier and it will also keep diseases at bay if the water is clean and trust me, diseases are a pain in the butt and way too stressful to deal with when in full time college/work/grad/undergrad all of that. My entire sorority right now is sick with some Columnaris that's untreatable with the older antibiotics that I have so I had to get a newer Anti-biotic called Kanamycin aka: KanaPlex by SeaChem. So that's been extremely stressful for the last week and a half and can only imagine how that would be if I had an entire dissertation or thesis to work on! Granted it's easier with only one fish as opposed to the 29 that I have...but...yeah you know XD
So anywho, twice a week will be the best thing for him and his healing tail. Also you use water conditioner I assume? If so, what kind? There's one called Stress Coat that contains aloe vera that will actually help damaged fins regenerate and heal up so that might be something good to look into as well