Can you temporarily move the plants, fish, etc... to a smaller tank or plastic container with a filter / airstone? Once you do that, you can change out the gravel.

I don't have another tank. Can I take just a little bit out at a time? I've been trying to think of a way, like to section it off a little at a time, and replace it. Would that work? Thanks for any suggestions :) Christy

if you have a plastic storage container (anything that holds water), especially a low vessel with a good surface area, you could use that.

The section at a time scares me a bit because that will likely stir up whatever wasteproducts that have been lodged in the gravel and make it harder for the fish to breathe. It's kind alike someone sweeping a layer of dust in a small, enclosed room - lotsa sneezing and wheezing...

I would strongly recommend finding a temporary place for the fish, with at least an airstone. Then get it all done in one shot.

Thank you, I'll do that. With doing it all in one shot, will the tank need to be cycled again? Should I rinse and/or boil the gravel before I put it in the tank? Thank you again! Christy

No need to re-cycle the tank as long as you are using the same filter medium. The bacteria action is taking place in the sponge or filter fluff or bio-wheel... that you have been using, as opposed to the water. I proved that while working for a wholesaler. We had a shipment of saltwater invertabrates and one apparently didn't survive the night, causing a chain reaction of death, cloudiness, stink... I drained all the water and mixed a new batch. The tank was fine, because I didn't change out the media. Conversely, I set up a new tank, at a different time, and used "good" water from various tanks, along with a brand new outside filter. I proved that good water wasn't the answer and that a new filter needed too go through the cycle.