Also, if you have: cut back on your lighting, kept up with water changes, and been cleaning off the algae as others here have been suggesting, you could try one more thing that I have found to be effective to control algae. Try dosing your tank with flourish excel (made by Seachem). The best way I can describe this stuff is to say it is a type of liquid CO2 for plants used by many who do not want to add a CO2 system to their tanks.
I recently tried this stuff in one of my tanks and it worked perfectly. I had added 3X the recommended dose and 90% of the algae was gone in 3 days. As you don’t have any plants in there, I would not exceed twice the recommend dose.
if you have a bubbler on your tank (didn’t see on in the pic) or your filtration system
breaks up the surface of the tank water to oxygenate it, you should not have to worry about your fish not getting enough O2.
It might be worth trying for your tank.