trigger proof cleaning crew--cowries and others

[wooden_reefer]

Is there such a thing?

I was told that cowries may be. First are they trigger proof?Second, do they release toxin?

Are they common, easy to get?

What else can be regarded as trigger proof cleaning crew that consume algae. The bottomline is to be able to keep triggers without having to clean algae off the glass, at least much less often.