I've had my 30 gallon tank set up for 3 1/2 years. For a long time I had three curviceps. One of the three died after 2 years and the other two have recently passed on. I also originally had 4 otos, 7 rummy nose, a bristlenose and a clown plec. I'm now down to 1 oto, 3 rummy nose, and the...