I know what you mean about that green old algae. First you should make sure that there is no sunlight hitting your tank. Purchase four turbo snails for every 20 gallons you have. Purchase a medium Algae Blennie
(Salarius fasciatus) and if you can afford it in the fulture, get yourself a Diatom filter once a month you can run a Diatom filter for four hour and you will remove the algae from your tank.
I haven't seen green or brown algae in my tanks for almost a year now. Let me know how it turns out for you