Bottom feeders for a smaller tank?

Hey I have a 30 gallon tank, and honestly nothing seems to live in it. We've had the water perfect, but over the years only a select few kinds of fish seem to live. Right now we have 6 yoyo loaches, and have had them for a few years but we need an algae eater. Plecos, no matter what kind, don't live too long, in my 100 gall tank our 3 plecos are doing amazing, so is there a good alternative to a pleco? Thanks a lot, also when I say nothing survived it is that our tank has been good for sometime now and nothing is wrong with it, I seriously have no idea why lots of our fish used to die.