So, this didn't happen in any of my betta tanks, but rather the 75G, with my husband's 12in Black Ghost knife. Here we are, he's playing video games, and we hear this popping noise, twice with a bright flash, not sure whats going on, trying to figure it out, we sit down. Then he happens to be looking at the fish time, and the same popping noise, and a bright flash again. He noticed his heater, immediately we unplugged everything, and took the header out. I did a quick water change with what water I had set aside for some betta tanks. Sooo about 3G's worth, + some extra w/ water conditioner. But I don't have 75G's of water hangin around.. Are there chemicals I should be worried about, anybody else had this happen? I'm freaking out, the fish are acting normal, like nothing happened, not even swimming frantically... IDK what to do!