Your above canopy looks really great. Canopies have been going out of favor, but I like them because my eyes don't like the lights needed for my corals. I also like them over covers as I feel it better gives surface airflow but I really just like having 'my business' covered on top.
Hearing MDF in association with an aquarium build, I just have to share this thread:
Forest Plywood explains two different approaches to “waterproofing” MDF so it can stay protected and withstand moisture in high humidity areas. Learn more!
forestplywood.com
Anywhere it gets wet, I avoid MDF yet an upcoming kitchen remodel has beat up thermofoil cabinet doors that we'll peel, fix & sand and then prime, prime, prime and paint, paint, paint the underneath MDF to seal it (because we are cheap and can't afford replacing cabinet doors).
For maintenance and cleaning, I find having doors that open (or remove) in front (and sides) is easiest. My FOWLR tank has a canopy I have to lift to feed and do maintenance, and it has been getting really annoying as it is heavy. Looks nice because it is streamlined appearance from the front. My mixed reef canopy (and even stand) has support infrastructure posts, but is sheathed in 1/4" plywood with 1/2" plywood front likely because there are three doors that open in the front facing canopy to crawl in to do aquarium maintenance or feeding is easy by just swinging open a door. That 1/2" plywood just gives the hinges something to bite into and because of the 3 front large openings, that 1/2" plywood is really all cutaway (think the facing trim of some kitchen cabinets, similar to that).
