It's OK - you can ask as many questions as you want. This is why this forum exists

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How large is your tank and how long have you had it? How long have you had the pleco and how large is it? If you have a testing kit, what are your ammonia, nitrite, and nitrate readings?
As for the "algae in the filter" ... are you sure they are algae? Perhaps it's slime? Unless you have a lot of light over your filter, I don't think you should have algae in it. Algae need light to grow, just like plants. The slime can be greenish in appearance. So perhaps you have confused it with algae?