I bought a sick fish(from a pet store that I have since learned has a reputation for selling sick fish) a while ago and it died within 48 hours. I transferred the old plants (after rinsing them) to a new 2.5 gallon tank, added a tetra 50 watt heater and bought a new fish, which, surprise, surprise, died within three days. When each fish got sick, this slime would appear, looking almost like strands floating in the water. After rinsing everything yet again, I bought a third fish, very healthy looking, and this guy made it a record four days. Needless to say, I almost gave up on keeping fish. I now have two healthy bettas(which I have housed in new aquariums), and am preparing the original tank for a third. I bleached it in a 5% bleach solution 10 days ago, tossed the plants, and let the tank sit for 4 days. Also bleached the heater. I then filled the tank with dechlorinated water, added new gravel, and the bleached heater. After 5 days, I noticed that some really slimy slime had accumulated on the inside of the tank, especially the heater. This slime isn't visible in the water itself (though the water looks cloudy) but can be felt. It doesn't appear to be algae. I am a bit reluctant to add the little betta and doom him to a certain death. Any suggestions on what to do? Do I need to chuck the whole set up, or can I treat the tank/heater in a way to finally get rid of this slime? Thanks for any help!