I never had an issue with gleba enemies.

You just don't kill the little nests.

They can't expand the same way biters can, they only expand to wetlands, not dry, and obviously not water, which means (at least on my world) they tend to cluster, and some areas just can't get an expansion from one wetland to the next.

That wetland rule seems to just be true for expansions, the original nests will be on dry land, but once cleared, they can't expand back to those spots.

I ended up sending a few souped up laser turret spidertrons to remotely manually clear out a bunch, and they just failed to generate back. I did have to kill a ton of nests, but by leaving the little nests, they don't expand back, and little nests can't send out expansion groups of their own.

Pain in the ass to save the little nests while killing all the big ones, but definitely worth it. Gleba is the hubworld now, every planet except aquilo can go directly to it and back.

I just wish I could send stuff ship to ship, but gleba's resources (except stone) are infinitely renewable anyway, rockets arent a problem once it's set up.