The Spider plant is one of many plants that will (probably - all terrestrials need different conditions!) do better on your desk than in your tank. They can adjust to aquatic life for a few months or so, but just rot after that. Unfortunately, once they've been in the tank for a while, they can't be 'rescued'. My recommendation is to buy terrestrial plants for terrestrial environments in the future!
With Java moss, you tie it down to the wood. Grafting is when you cut a stem from one plant and put a piece of another plant to make the plant on top do better. It's common to do this with cacti - indeed one of the plants in my cactus collection is grafted! I am such a perfectionist today.

