Algea eaters

Agreed. If the main issue is green spot algae on the glass, then nerites come out tops. Ottos are better for diatom algae on glass.
Some wiping might still be necessary (some tanks more than others).

 

The best algae eating fish that I have had was my Golden Nugget Plec.
They also need a decent sized tank, and slightly warmer water than standard trop temps. And soft water

 

Zebra nerites get about 2,5cm. Horned nerites about 1cm. They don’t breed in freshwater so won’t multiply.
Liquid CO2 eg Seachem Excel helps with algae by (aot) promoting plant growth that then outcompetes algae for nutrients. But I don’t think it’s an either-or thing. Get some cleanup crew anyway.

 

If you can’t find at your local stores, try courier them in eg via Aqua Empire or McMerwe. Both are painless to deal with.
PS nerites can die when they land on their backs as they struggle to turn themselves around. So take care when putting them in the tank, and if you ever see one that has fallen down, help him to turn back. They also occasionally wander out of rimless tanks, so keep an eye out for that. A dead nerite will smell bad, that’s how you know. They sometimes hibernate for a bit which is scary as they might look dead. As long as they don’t smell, put them back in the tank and leave them alone / observe.

 

But hillstream loach is not suitable for small tanks and need high flow.