I never have to take out the sand to clean the tank, sometimes i'll stir it up a little with my hand before a waterchange and that's it. This sand settles very quickly.
And the fewer animals in the tank, the less waste, first I had a lot of guppies and there was much more waste on the bottom, but occasionally the turtles ate one of them. And now there are less guppies and also less waste. Actually the only waste on the bottom of my tank is from the guppies and shrimps (tiny poops)....
I think the pleco is helping to get rid of the turtles waste but he/she won't clean up his/her own waste.
I always used to think that sand turns in to mud, but if you use the right sand it just acts like rocks, but very very tiny rocks, haha
