I pull the clumps apart, so the light goes thought the whole clump evenly, and it fills back in the gaps left from pulling it apart.
I then removed the excess/culled plants, but made sure I saved the little critters that might still be attached, and add them back to the tank.
When I was actively maintaining my algae scrubber, I had the best experience with my plant removing nitrate (along with other nutrients), by removing plant growth completely from the system.
I traded it in to the LFS.
It was Prolifera, not cheto, but I would assume the outcome would be similar.
The easiest / best way to get rid of chemical concentration is water changes.
Do a 20 gal water change, if your system is a 55 gal. or calculate that same volume for your sized tank.
In college, I ran a Prolifera alge scrubber on a heavely stocked fish only system, with some mushrooms and xenia for decorations, as an experiment. You need ALLOT of fast growing plants to keep up with an efficient nitrate removal system. I had approx 2 gallons of prolifera in my system at any time. I was able to keep it down around 2 to 5ppm, without doing ANY water changes. I ran this setup for approx 1.5 years.
It was basically a large refugum.
NOTE: When I say approx 2 gallons, I mean volume of plant...meaning if you cut open a plastic gallon milk container, and filled it with plant, packed in tight with zero water.
I replaced evap with ro/di, and added minimal "RED YELLOW AND BLUE" and fed only Spirilna20 (my fav high quality flake food)