overstocked?

not overstocked but poorly stocked. if you're not having problems yet, you will soon. rainbow sharks don't tolerate more than one in a tank unless that tank is quite large. chinese algae eaters eat less and less algae as they mature (eventually they eat none) and are active in attaching themselves to other fish and sucking off their slimecoat.

use a razor blade ... carefully.

your rainbow sharks will also go after your SAE. Take out 1 rainbow shark and the SAE.