Java Fern should not have its roots planted in gravel. It is best tied to a rock or some wood and left to attach. You can use cotton, fishing line or dental floss (use one that isn't flavoured).
Hair Grass doesn't do well under water and will probably die within a month. It should have its roots planted in the substrate and the leaves out of water. You can leave it in the pot and get a piece of polystyrene foam. Cut a hole in the foam and put the pot in it. Then let the plant float around the tank. The roots will be wet and the leaves will be dry
Hair Grass doesn't do well under water and will probably die within a month. It should have its roots planted in the substrate and the leaves out of water.
Are you sure of this Colin? Hair grass is a generic name, but usually refers to Eleocharis acicularis or E. parvula. Here is my E. parvula doing OK underwater: