Welcome! I'm new to this forum as well, but I kept fish and planted tanks for a good while in the past and have recently returned to the hobby. The axolot is pretty wild looking. The hornwort is mainly a tough floating plant. Glad it's doing well for you. I always have a tendency to recommend Java moss, Java ferns, and Anubias. There are a lot of types of each, but they don't get planted in the substrate, gravel, etc. They're tough, low light plants that are easy to grow and they just get attached to a rock, a piece of driftwood, or even a decoration if that's what is used. They can be attached with thread or a rubber band and by the time those start to disintegrate the plant is attached on its own. A newer, sometimes simpler way is using a little dab of super glue gel to attach the plant rhizome to whatever structure. It dries quickly and is completely safe for the fish. I've researched it and have experience with it myself in fish tanks with small fish and even in shrimp tanks, with no problems. I think on this forum I've seen people talk about buying plants online from aquarium plants.com and aquarium co-op. Both of those, I know, come highly recommended. To save a buck and get a lot of 'buy two get one free' deals, I've used the aquarium plants factory. However the name sounds, their plants have always been exactly like the ones pictured; healthy, hardy, and rather inexpensive, as well as good service and quick shipment. I should say, I don't have any affiliation with them other than buying their plants a couple of times and being completely satisfied. Not even sure if I'm allowed to say all this on this forum but, oh well, it's all true. I hope it goes well for you and your really cool looking axolot.