I bought gravel that was relatively cheap from Walmart (maybe about a year ago) and I just recently bought two guppies (Friday.) When I use the net and try to catch my fish for a water change, they gravel flakes off in to tiny specs that float around my tank (tank is 1 gallon.) I'm worried because one of my guppies is acting strangely. One half of the time, she floats around the top, and stays in a corner. The other, she's at the bottom, and still in a corner. Should I change to a different gravel that doesn't flake off?