I would do at least once a week 50% removing any waste on the bottom with that filter configuration. Rinse the aquaclear sponge every other week or so (don't worry, these are the easiest filters to clean).
My biggest issue with AC 70's is that with larger fish they tend to get gunked up rather quickly requiring more cleaning, and with the smaller motor size the impeller shaft is far easier to get jammed up during a power outage than an AC 110. Even when I had 55 gallon tank set ups I used two AC 500's (110's) for just that reason. I got tired of constantly having to pull the AC 70 motors to clean the impeller wells & shafts. A great filter for smaller tropical fish, but IME not suited for larger cichlids.
BTW - the actual listed "manufacturer" turnover rate of most filters (certainly AC filters) is based on 0 media, and zero mulm/waste. So now factor that into your turnover equation. With media in place, and build up from waste, an AC 70 probably won't be turning over more than 150-175 GPH.
The link that you posted to the male zz red dragon, is this the fish going into the 55 gallon, with a single AC 70?
If so, you are sadly mistaken to think that filter, in that tank, is going to keep up to that fish as it matures.
For a starter I wouldn't keep an adult male fish like that, which has the potential to reach 12+ inches, in a 55 gallon tank. And even if I was inclined to do so, I would never run a single AC 70 on the tank, even if I was doing 50% water changes twice a week.
What you are attempting to save in filter cost and power, will be spent in labour as that fish matures. An AC 110 consumes 14 watts in power, in the grand sceme of things a small price to pay, even if two of them are running in tandem. Some of my AC 110's (formerly AC 500's) are 15+ yrs old, and other than a few impeller changes along the way (mostly from sand damage) they are all still running as smoothly as the day I started them.
The one in your avatar also has the potential to easily reach 12+ inches, so either way you are pushing the limits across the board. Good luck with whatever you decide.