What's on my plants ?!?

Hello!

About 6 months ago I bought two different kinds of plants. I do not remember which ones, but I know they were on the list of non-dangerous plants for axolotls somewhere on this forum.

Today, I noticed some kinds of white "filaments" hanging on plants. Sometimes, they drop out and float in the aquarium (the filter picks them up later). I wanted to know if it was normal, since my little Croissant loves to play in plants?

I also have very tiny snails (less than 2mm) walking around the tank, but I do not think that's the cause.

Thank you very much!

The first picture shoes hydra. I had these for a while in one of my Japanese Firebellied newt tanks, I added Greater Pond snail to their tank and they munched their way through them. I can't quite tell in the second picture what it is.

If I remember, it is anubia and java fern (I'm not sure though...) I checked on that website and I chose plants on there list: https://www.caudata.org/axolotl-sanctuary/Aquascape.shtml

Normally, I do a 30% water change each week. Croissant is feed with big red worms (1 per day). The only way I see who I have this is because its excrement mixes with the sand. So I can not remove them all. How could I clean the sand more efficiently?

Also, snails are a luxury dish for Croissant. He always tries to eat the big snails, so I can only put very small snails on him (I already caught him with a snail bigger than his head in his mouth). However, I believe that snails are too small to do the job effectively.

Both pics look like hydra to me. They're a common aquarium pest, often hitchhike in on live plants. They are (mostly) harmless to most adult fish, but they do sting, and I can't imagine that, with their soft fragile skin, hydra stings feel nice to axolotls. Molly fish will also eat hydra quite effectively. Croissant might also eat the mollies, but at least he'd have to chase them first.

If there are only a couple of hydra, you can probably just scrape them off by hand. You can soak non-porous aquarium decor in a 10% bleach 90% water mix for 15 minutes and wash THOROUGHLY and air dry before putting it back in. There is a method of ridding aquariums by keeping the temp in the aquarium basically at boiling point for a set period of time, but I've never had hydra so I haven't had to actually do it and you obviously couldn't leave your axolotl in the tank. I know that Fenbendazole will also kill them, but it is probably not safe for axolotls so I'm not sure how you'd effectively use it, someone else would have to answer that.