I disagree; Using a HOB to diffuse C02 works far better than an actual ceramic diffuser.
With a HOB, it disperses C02 more effectively throughout the water column as the impeller munches up the bubbles.
Using a diffuser, bubbles go up and pop in the atmosphere.
A reactor is the best solution, although it takes a fairly small one with DIY.
I personally have one diffuser on a 29 gal and one reactor on an 80gal . The remaining seven planted tanks use a HOB as a diffuser.
Idk FTM, i tried looking at the inside of my AC filter once the bubbles go to the impeller and you can see once they reach the impeller area they are chopped up by it but then escape through the hole which is right by the impeller.