Seachem Flourish 膠水

The gel is thick enough that it doesn't run everywhere when I'm pressing moss onto driftwood, and a single tube has lasted through three tank rescapes. Cured clear within a minute, so I didn't have to hold the plant in place forever.

This stuff bonds underwater in seconds, so I didn't have to drain the tank to attach my moss to the driftwood. It's a thick gel that doesn't drip everywhere, and a tiny drop held a whole bunch plant firmly in place.

I was skeptical about gluing plants underwater, but this gel held a java fern tuft to a rock instantly and hasn't let go after two weeks. The thick consistency makes it easy to dab exactly where you need it without making a mess.