You can get a nano diffuser and stick it down low over a lot of foliage. The tiny bubbles will have the maze of leaves to navigate before hitting the water surface. A lot of the bubbles stay on the underside of the leaves for a while so aids in co2 absorption. If the path to the water surface hits water flow (like spray bar or hob water outlet), may help push those bubbles around a little longer too. Alternatively, just stick co2 outlet into filter intake or let it bubble into the intake.
