Is One Enough?

[Juxtaroberto]

Here is why it's a bad idea:

Any pleco makes more waste than most other fish.
Algae problems are a sign of an underlying problem, most likely high nitrAtes. Adding to the bioload will just compound the problem, by adding more nitrAtes.

Change your water, clean out the filter sponge/pad in dirty tank water, banging it against the side of the bucket/brick wall and vacuum your gravel.

Exactly. Furthermore, the pleco will eat the algae... and poop out waste which will add to the nitrogen cycle, which will result in more nitrate... which will cause algae problems, ad infinitum.