I agree with the two posters above. I too use large smooth river rocks to anchor my plants. I have a bare-bottom tank. If you want something visually pleasing, follow the suggestion of using one of those stick-on tank backgrounds on the floor of the tank. There are heaps of different designs and some of them would look fine on the floor.
If you do use sand, you can minimise the risk of axies swallowing sand by feeding them from above, training them to take earthworms from your hand or being dropped to them, or using a feeding dish. Even adult axies will root around in the sand for food and can swallow quite a lot of it.