Hi.Congrats on the New Pleco.

What size is he,and what type? Pleco's are known for not dealing too well with salt,so if you treat him with that,you want to do it very slowly,and keep a watchful eye on him.To actually get rid of the Ick,you'd have to treat him at .03% for a substantial length of time,and alot of Pleco's don't handle that strength well/if at all. You can try something like Quick Cure which works well.You also have to be very careful using anything with Malachite Green/Formalin,because they too can be somewhat tough on the smaller Pleco's. Anytime you use those types of Meds, you have to cover your tank with something like a towel,as light makes the Meds ineffective.Let me know what kind/how big,and treatment you're thinking of doing & we'll go from there.