Help- pretty sure my Betta is uprooting the plants - would a Marimo Moss Ball be better?

[RhubarbRhubarbRhubarb]

I haven't come across any info regarding Betta's digging up plants but he seems to be doing it.
He can't manage the Anubia as its so big but i wondered if the Marimo Moss balls would be better?

Can anyone recommend a good online supplier?

Have you seen him doing it? What plants are being uprooted? Moss balls would be fine with a betta. I've never got a moss ball from Plants Alive but I've had other plants from them and they've been fine.

Well, no not actually seen him doing it but not sure how else its happening. They are Cabomba Caroliniana and i planted them securely.
We've had them for ages and its only recently been happening.

How long are the roots and what substrate is it? Some plants can be a bugger to get them to stay put and even a fish swimming past can dislodge them.

The roots are pretty long, I've seen some up to 4cm.

The substrate is natural gravel like this

Maybe it is by accident. I hadnt thought of that.

Don't know about the moss thing but I've stopped my corys from digging up the plants by putting 2-4cm pebbles around the roots.