So, I kind of want a 3rd betta... But I'd need to buy a new tank and stuff. Now, I have a bag of roughly 5 lbs of gravel that I'm wondering if I can use instead of buying new substrate. My only issue is that it was in my 5.5 gallon tank when my topfin heater leaked toxins into the water and killed Severus. It's been out of the water for about three weeks now, so I'm wondering if it anything nasty on it would have evaporated and it's safe to use. What do you guys think? Is it safe or should I just get new substrate if I end up getting another fish?