30 gallon. clear blue filtration. ID, 2 angels, 3 tetras, guppy, Molly (cuz one died two weeks ago), dwarf frog, zig zag eel (tiny), pleco (just died). 7.0 pH 78-82° zero ammonia. Don't test nitrites/ates 6 month old tank. Lightly planted. 20% changes once a week. One angel growing quickly. ID shark doubled in size the last month. Molly died. No visual signs of problems physically or otherwise. Fine.. five minutes later dead. A week later my pleco starts acting odd. Hardly moving and not eating his wafers. A week after that he is upside down bottom of tank. I flip him over, he's not swimming away but alive. I quarantined him and ten hours later he's alive but upside down again. I flip him over and he moves around a little. Few hours later he is dead and turning white.. tank problem? Disease? Random Molly death and starved pleco from lack of veggies? Overcrowding?