We had the tiels for about a year and a half before our kitten arrived and it was a horrible transition that caused me to regret adopting her in the first place
Alaska is a very active and quite aggressive kitten who has zero contact with the tiels as I could never ever trust her. We bought a bigger and very sturdy cage much higher from the ground but she is never alone in the same room as the birds.
The birds now have their own room (we had a door installed in our front sunroom) and the birds have their out cage time in there and they sleep in there.
The kitten was jumping almost two metres from the ground to get on top on their cage at night while covered and they were having night frights because of her
Cats are just too fast. We have the spray bottle on hand at all times!
She is 10 months old now and is slowly settling down but I will never trust her.
30cm is really close to floor and I would be looking at a way to put a safety barrier around the bottom of the cage and never leave them alone in the same room because as discussed, the cage does not mean they are completely safe.
Be on guard at all times as it is just not worth the risk. It only takes one little swipe of a cats nail to lose your precious bird.
I wish you good luck in finding the methods that work best for you and your household
It's hard to be an animal lover but keep animals who can't all love each other.