AQUANEAT Small Fountain Pump, 50 GPH Mini Submersible Water Pump with 3.3 ft Tubing, for Aquarium Fish Tank, Pet Water Fountain, Hydroponics, Pond Waterfall Filter Pump

I would suggest a very tiny submersible pump (like this one https://www.amazon.com/AQUANEAT-Submersible-Fountain-Aquarium-Hydroponics/dp/B0BLY39XW4?th=1 ) that sits directly above the diffuser, so it acts as a mixing chamber and pushes CO2 horizontally across the plants before the bubbles go up. If it still disrupts too much, put it close to the back, so you get the flow on the lower part but not in the middle of the tank, see if you can get it to push the CO2 towards the plants that demand most CO2, and I would also say on the opposite side of the sponge filter, so water flows to the filter across the entire tank. I actually have one of those in my 40G, because though I have some Koralia Nanos doing the general flow, I think one tiny pump above the diffuser acts as a mixing chamber right as the gas comes in.