they are acrylic safe, they eat up everything, left over food, algae they are super friendly and if your turtle isnt agressive towards your rays im sure they pleco will be safe. they will eat wood but not wood eating pleco more veggie, algae type
I reduced down my lighting to 6 hours a day and this has seemed to clear up the issue. I think I might add in a couple lower watt white 'moonlight' type lights so they get a little more lower light levels for more hours per day then dark for 18 and light for 6.
if really want, can put in UV and that should clear the problem.