Jack Dempseys will most tear up Vallisneria. They might tear at anubias on driftwood, maybe not. You mentioned an oscar? Oscars will almost definitely uproot any plant.
What kind of algae? Is it brown or green?
There are two different 55g tanks. One has a single 5in oscar. She has been in it with Java fern and Amazonian swords and has not bothered them at all in the 4 months I have had her. Her tank is getting rescaped to look like a flooded mangrove. I have some manzanita wood that shipped out today from Mazman in the vendor section.
My other tank has a pair of 3in JDs in it. It had a common pleco in it till just recently I rehomed it since it has already tripled in size,was a surprise gift from my roomate on my birthday. The JDs have been in with swords, crypts and java ferns since I got them 4 months ago.
These 2 love to swim around and thru the stems of the plants.
Here is a shot of the algea.
The light I have on this tank atm is a 2ft Fluval Aquasky led, it came with the tank (its a 3rd hand Truvu acrylic I got for free). It leaves the ends dark so the algea growth is only in the area that gets light. It looks brown to me, tho I could be wrong, as I just got back into keeping fish after about a decade away from the hobby. The pleco I had in there kept it knocked down but I rehomed it earlier this month due to its final adult size and was afraid I wouldn't be able to get it out of the smallish holes on top of the acrylic tank (since they can get to 17in)