I would use plain soil. Potting soil would be too light. I would just take a knife or saw and saw sections of the present pots, then repot them in soil. These types of plants are pretty forgiving.

thank you for your quick response and the information,when you say plain soil do you mean garden soil or something else?

There is actually potting soil for ponds you can buy. Check at a garden nursery that sell pond supplies. Pond planting soil is heavier.

thank you too, for your response.will check it out.

Avoid mixes based on peat moss or that contain Perlite.

I just use plain garden soil. You don't want anything that will easily float out of the pot. I don't even cover the soil with stones and have no problem with it floating out, with the plain garden soil. I fertilize them once a month.